Mobile Lab Manual

EC - 705 Mobile Communication Page No.:

Date:

PRACTICAL # 1 AIM: To study the various components of GSM kit and understanding RF module APPARATUS: Dual band GSM antenna, Connectors, Test points & boards, GSM-EVAL kit

GSM-EVAL kit includes following components: • Evaluation board (A2D/F35/C2D) • F35-A-2: TC35 Module with IMEI No. • A2D/F35/C2D evaluation board PCB • GSM antenna and cable with coaxial plug (30 cm) • RS-232 9 pin serial cable. • Head set with RJ-45 plug • Wall mount paper adapter • A2D- test software and hyper terminal windows s/w • Other extra accessories

THEORY: 1. Evaluation Board (A2D/F35/C2D)

The evaluation board below called EVAL board consists of two main components first; one is the F35 module, which is not part of the hands off extras. The communication with GSM mod-ule is made by serial links using the GSM at command set.

The A2D and F35 modules have their own SIM cardholder. Module has an antenna connector and a 40-pin connector. The second main component is the real EVAL board connectors at the front side. One of them is a 9-pin plug socket for terminal connection and the other one is an 8-pin connector for a head set. The last one is the power connector. The connection to the module can be done by an adaptor PCB, the corresponding connector is at the top of the EVAL board.

Technical data: Dimensions: 170×110×40 mm Power supply: 10.8+0.18 v Current consumption: Max 20mA (at 12V w/o module) Operating Temperature: 0 to +40°C Storage: -40 to +85°C SIM cardholder for small SIM cards Audio interface for loudspeaker and microphone RS 232 / V24

2. F-35-A-2:TC35 module with IMEI number

The GSM module (Global system for mobile communication) F-35 is a mobile station for transmission of voice & data calls as well as short messages (SMS- short message service) in GSM network.

Changed with the DEMO VERSION of CAD-KAS PDF-Editor (http://www.cadkas.com).




Technical data: GSM data service: 300-1400 Bps, asynchronous, transparent and non-transparent. (V.1,

V.22, V.23, V.22 bis, V.26 ter, V.32, V.34, V.110) Dimension: (LXWXH in mm) 83× 50.5×11.4(dimension with mounting brackets) 82×50.5×11.4(dimension without mounting brackets) Weight (in gm): 54(without i chip) 59(with i chip) Temperature range (in °C): Operation: -20 to +55 Operation with I chip: 0 to +55 Storage: -25 to +70

3. RF characteristics:

• Receiver: EGSM sensitivity: <-104dBm • DCS sensitivity: <-100dBm • Selectivity@200 kHz: >9dBc • Selectivity@400 kHz: >41dBc • Dynamic range: 62dB • Intermodulation: >-43dBm • C-channel rejection: >9dBc

Transmitter: • Max. o/p power (EGSM): 33dBm +/-2dB • Max. o/p power(DCS): 30dBm +/-2dB • Min. o/p power(EGSM): 5dBm+/_5dB • Min. o/p power(DCS): 0dBm+/_5dB • H2 level: <-30dBm • H3 level: <-30dBm • Noise in 925-935 MHz: <-30dBm • Noise in 935-960 MHz: <-79dBm • Noise in 1805-1880 MHz: <-71dBm • Phase error at peak power: <5°RMS • Frequency error: +1-0, 1PPM max • Supply voltage(in VDC): 3.6-5.0 • Avg. current consumption(in mA/5v nominal)

22 mA*/5v power mode1 (idle) 260 mA*/5v power mode2 (power level 5i max) 21 mA*/5v power mode3 (power level 7)





4. GSM antenna & cable with co-axial plug (30 cm) (Operating freq.: 900/1800 MHz)

Your modem is actually a low power radio transmitter and receiver. It seems out & receiver radio freq. energy. When you use your modem, the cellular system handling your call controls both the radio frequency & the power level at your cellular modem.

5. RS-232 9 pin serial cable:

CCITT Pin Description Direction 102 5 Signal GND In 103 3 TxD Out 104 2 RxD In 105 7 Request to sent Out 106 8 Clear to send Out 107 6 Data set ready In 108 4 Data terminal ready Out 109 1 Data carrier detect Out 125 9 Ring indicator

Default transfer parameter

• Transfer rate 9600bps • Echo on • 8 Bit none parity, 1 stop Bit

6. Head set with RJ-45 plug

Specifications of RJ-45 • Vcc 12 DC • RxD(optional) • TxD(optional) • GND • Speaker OUT+ • Speaker OUT- • Microphone In+ • Microphone In-

CONCLUSION:





Date: PRACTICAL # 2

AIM: To study the GSM Architecture THEORY:

As shown in the figure, the GSM system comprises of the following units: • Base Transceiver Stations • Base Station Controllers • Mobile Switching Centre • A set of registers (databases) to assist in mobility management and security functions

All signaling between the MSC and the various registers as well between various MSCs take place using the signaling system 7 (SS7) network with the application level messages using the mobile ap-plication protocol (MAP) designed especially for GSM. Mobile Stations (MS): The GSM mobile stations are portable radiotelephony. Units can be used on any GSM sys-tems as vehicular and / or hand held terminals power levels supported by the GSM mobile station currently range from 0.8 to 8.0 Watts and power supply techniques are used on the air interface to extend battery life. At the time of manufacture, an International Mobile Equipment Identity (IMEI), which cannot be altered or reprogrammed easily, is fed into the terminal. A Subscriber Identity Module (SIM) is required to activate and operate a GSM terminal. The SIM may be contained within the MS or it may be a removable unit that can be changed by the user. In the later case, any GSM terminal can become the user’s MS upon plugging in the SIM card. The IMSI (International Mobile Subscriber Identity) is programmed in the SIM at the time of service provisioning along with the appropriate security parameters and algorithms. Base Station System (BSS): The base station system (BSS) comprises of a base station controller (BSC) and one or more subtending base transceiver station (BTS). The BSS is responsible for all functions related to the ra-dio resources (i.e. channel) management. These include the management of radio channel configura-tion with respect to the speech, data or signaling channels, allocation and release of channels for all setup and release of channel control of frequency hopping and transmit power at the MS. The ranges of functions performed by the BSS therefore include the following. Radio Resource Control:

• Configuration of radio channels • Selection, allocation and de-allocation of radio channels • Monitoring radio channels’ busy / idle status • Encryption of radio interface

Frequency hopping and power control:

• Assignment of frequency hop sequence and start time • Assignment of effective radiated power (ERP) to mobile station





Call Hand-off management: • Collect signal data from adjacent BSS • Analyze signal quality data and determine hand-off need • Keep MSC informed regarding call hand-off activity

Digital Signal Processing:

• Trans-coding and rate adaptation • Channel coding and decoding

The BSS functions are partition into a BSC & a BTS. Table given lists some of the functions and / or physical elements located in the BSC and BTS.

Base Station Controller (BSC) Base Transceiver Status (BTS) BSC processors control BTS radio resource management hand

BTS processors radio transceiver equalizers channel codes. Trans-coders encryption unit interleaving add / interleave combine pro selectors

Mobile Switching Centre (MSC): The mobile switching centre (MSC) for GSM can be viewed as a local ISPN switch with ad-ditional capabilities to support mobility and management functions like terminal registration, loca-tion updating & hand-off. Further, unlike a local switch in a fixed network, the MSC does not con-tain the mobile subscriber parameters. Thus, the MSC performs the following major functions:

• Call setup, supervision and release • Digit collection & translation • Call routing • Billing information collection • Mobility management

o Registration o Location updating o Inter BSC and inter MSC call hand-off

• Paging and altering • Management of radio • Resources during a call • Manage collections of BSS, other MSC and PSTN / ISDN • Interrogation of appropriate registers (V / HLR)

Home Location Register (HLR): The HLR represents a centralized database that has a permanent data fill about the mobile subscribers in a large service area. The HLR is kept updated with the current locations of all its mo-bile subscribers, including those who may have “roamed” to another network within or outside the country. The routing information is obtained from the serving VLR or a call by call the HLR queries the servicing VLR for a MSRN.





Besides up to date location information for each subscriber, which is a dynamic, the HLR maintains the following subscriber data on a permanent basis:

• International Mobile Subscriber Identity (IMSI) • Service Subscription Information • Service Restrictions • Supplementary Services • Mobile Terminal Characteristics • Billing and accounting information

Visiting Location Register (VLR): The VLR represents a temporary data store and generally there is one VLR per MSC. These registers contain information about the mobile subscribers who are currently in the service area cov-ered by the MSC / VLR. The VLR also contains info about locally activated functions such as call forward on busy, etc. Thus, the temporary subscriber information resident in a VLR includes:

• Features currently activated • Temporary mobile station identity (TMSI) • Current location information about the MS

Authentication Centre (AC): Generally associated with the HLR, the authentication centre contains parameters that can be used on initial location registration updates and on each call setup request from the MS. In case of GSM, the AC maintains the authentication keys and algorithms and provides the security triplets to the VLR; so that the user authentication and radio channel encryption produces may be carried at or within the visited network. The authentication centre of a GSM network contains security modules for authentication keys and the authentication cipher key generation algorithms A3 and A8 respec-tively. CONCLUSION:





Date:

PRACTICAL # 3 AIM: To observe various parameters concerning modern & SIM card hardware by giving AT commands. APPARATUS: GSM trainer kit, RS-232 cable, windows software, SIM card THEORY: Mobile Station & Subscriber Identity Module: Mobile station consists of user independent hardware for software & user identity module, which stores all user specific data. Mobile station can be identified by IMEI no. user specific opera-tions are SIM dependent & without is only emergency calls are possible. SIM Card contains:

• Identifiers & tables • List of subscribed services • Personal identification no. • PUK • Authentication key • IMSI No.

PIN: 4 digits & PUK: 8 digits On entering wrong PIN in succession, MS will lock. Then PUK is used for unlocking. Some MS can be comprises or other vendor specific functions like fingerprints. Network & Switching Subsystem: Every communication system in telecom depends on efficient network & switching subsys-tem. For GSM systems, MSC is important. It is used for inter network connection & via intra net-work connection as well every call from MS has to be route through MSC MSC has several functions &stores some imp information about every activated MS of area for that MSC. For this several database are connected to MSC. One such permanent database is the HLR.

• It stores all users’ info like MSI SDN No. Authentication keys, etc. • It updates location area of MS every time billing & account information • VLR is associated to MSC & is a dynamic database. It gives info about current location of

MS by which HLR updates location area information • Equipment Identity Report (EIP) is another database which stores IMEI NO. & other equip-

ment related info. Such as MS characteristics etc. are stored in EIR • IMSI: Assigned to a MS at subscription time. It uniquely identifies a given MS. It is a 15 di-

git no. It includes Mobile Country Code: 3 Digits Mobile Network Code: 2 Digits MSIN & NMSI (National Mobile Subscriber Identity) IMEI: It uniquely identifies the MS equipment contain 15 digits.





It carries: Type Approval Code (TAC): 6 DIGITS Final Assembly Code (FAC): 2 DIGITS The Serial No.: 6 digits A Sparse (SP): 1 digits MSI SDN: Standard for Mobile Subscriber International Subscriber Dialing Network No. It is of 10 digits RSSI: Received Signal Strength Indicator It detects the reverse voice channel signal strength, used to control power of each user, used to eliminate near-far end problems. OBSERVATION TABLE: Sr. No.

Command & Interpreta-tion

Possible Response Actual Response

1 AT+CGMI AT+CGMI = ? (Gives Manufacture In-formation)

Falcon - A2D - V101 OK

2 AT+CGMM AT+CGMM = ? (Gives GSM Model In-formation)

Multiband 900E 1800 OK

3 AT+CGMR AT+CGMR = ? (Gives GSM Model firm-ware Revision Informa-tion)

<Version Number> OK

4 AT+CGSN AT+CGSN = ? (Gives IMEI Information)

<IMEI> OK

5 AT+CIMI AT+CIMI = ? ( IMSI No.)

<IMSI> OK

6 AT+CCID AT+CCID = ? (EF - CCID File Informa-tion)

+CCID : < id > Defined Value: OK <Td>:EF - CCID File in Hex-adecimal Format

7 AT+CPIN AT+CPIN = ? (Command is used to send the PIN to the Modem Which is needed to Regis-ter in to GSM n/w)

+CPIN : < code > OK Defined Values : < code > : :Ready; Modem is not Pending for any Password. :SIM PIN; Modem is waiting sim pin to be given. :SIM PUK; Modem is waiting





simpuk to be given. 8 AT+CREG OK

Unsolicited result codes: +CREG: <stat> if <n> equals 1 +CREG: <stat>,<lac>,<ci>, if <n> equals 2

AT+CREG? +CREG: <n>,<stat> (n=1) +CREG: <n>, <stat>, <lac>, <ci> (n=2)

AT+CREG=? +CREG: (list of supported <n>s> )

(Command is used to show the n\w registration status & to control the presentation of an unsoli-cited result code +CREG: <stat> when there is a -><stat>: change in the n/w registration status )

Defined values: - > <n>: 0 : disable n/w regis-

tration unsolicited result code

1 : enable n/w registra-tion unsolicited result code

2 : enable n/w registra-tion unsolicited result code with <lac> & <ci>

- > <stat> : 0 : not registered, ME

is not currently searching a new operator to register

1 : registered, homework

2 : not registered, but ME is currently searching a new op-erator to register

3 : registered denied 4 : unknown 5 : registered, roam-

ing - > <lac> : string type, two byte

location area code in hexadecimal format ( e.g. “00C3” equals 193 in decimal )

- > <ci> : string type, two byte

cell ID in hexade-cimal format

9 AT+COPS=[<mode> [,<format> [,<oper>]]]

OK

AT+COPS? + COPS :





<mode>[,<format>,<oper>] AT+COPS=?

(Command is used to show the current & avail-able PLMN’S. It is also used to select a PLMN manually or automatical-ly)

+COPS list of supported ( <stat>, <long alphanumeric oper>, <short alphanumeric oper>, <numeric oper> ) Defined values : - > <mode> : 0 : automatic [<oper> field is ignored] 1 : manual [<oper> field shall be present ) - > <format> : 0 : string type,

GSM locatio-nared identi-fication number which consists of a three BCD digit country code. Coded as in ITU-TE.212 annex A[10], plus a two BCD digit n/w code, which is administration specific.

- > <stat> : 0 : unknown 1 : available 2 : current 3 : forbidden

10 AT+CSQ +CSQ : <rssi>, <ber> AT+CSQ=?

(Command is used to ask for the n/w field strength & the current bit error rate )

+CSQ : ( list of supported <rssi>s ), (list of sup-ported <ber>s )

Defined values : <rssi> : 0 : -113 dBm or less 1 : -111 dBm 2 - 30 : -109…….-53 dBm 31 : -51 dBm or greater 99 : not known or not detectable

<ber> (inpercent) : 0-7 : as RXQUAL values in the table in GSM 05.08 [20] sub clause 8.2.4 99 : not known or detectable





CONCLUSION:





Date:

PRACTICAL # 4 AIM: (a) To study call information and call setting commands. (b) To study various commands related to phone book. APPARATUS: GSM trainer, RS-232 cable THEORY: Supplementary services:-

GSM supports a comprehensive set of supplementary services that can complement & sup-port both telephone & data services. Supplementary services are defined by GSM & are characte-rized as revenue generating features. A partial listing supplementary services is as follows:- Call forwarding: The service gives the subscribe, the ability to forward incoming calls to another number if the called mobile unit is not reachable, busy, does not reply, or if forwarding is allowed unconditionally. Barring outgoing calls: This service makes it possible for a mobile subscriber to prevent all out-going calls. Barring incoming calls: This function allows the subscriber to prevent incoming call. The following two conditions for incoming call barring exists. Barring all incoming calls & barring of incoming calls when roaming outside the home PLMN. Advice of charge (AOC): The AOC service provides the subscriber with an estimate of the call charges. These are two types of AOC information: one that provides subscriber with an estimate of the bill & that can be used for immediate charging purposes. AOC for data calls is provides on the basis of time measurement. Call hold: This service enables the subscriber to interrupt an ongoing call & then subsequently rees-tablish that call. The hold service is only applicable to normal telephone. Call waiting: The service enables the subscriber to be notified of an incoming call during a conversation. The subscriber can answer, reject or ignore the incoming call. It’s applicable to all GSM telecommunication services using a circuit switched connection. Multiparty service: This service enables the subscriber to establish a multiparty conversation i.e. a simultaneous conversation between 3 & 6 subscribers. Applicable only to normal telephony. Calling line identification presentational restriction: This services supply the called party with the integrated services digital network (ISDN) of the calling party. The restriction service enables the calling party to restrict the presentation. Restriction over rides the presentation. Closed user grounds (CUGS): CUGS are generally comparable to a PBX. They are a group of sub-scribe who are capable of only calling themselves & certain numbers.





OBSERVATION TABLE: Sr. No.

Command & Interpre-tation


1 AT+CR=[ ]0 AT+CR = 1 AT+CR ? AT+CR = ? (Command controls whether or not interme-diate result mode +CR:<serv> is return from modem during connect negotiations of data call)

Ok ok +CR:<mode> +CR:<list of modes> <mode>: 0; disable reporting 1; enable reporting <serv>: ASYNC; asyn-chronous transparent REL ASYNC; asynchronous non transparent

2 AT+CRC = [ ]0 AT+CRC = 1 AT+CRC ? AT+CRC = ? (It controls whether or not normal RING msg of call indication using un-solicited result)

Ok ok

+CRC:<mode> +CRC:<list of modes> <mode>: 0; disable reporting 1; enable reporting <type>: ASYNC; asyn-chronous transparent, REL ASYNC, asynchronous non transparent voice, normal voice

3 AT+ILRR = [ ] 0 AT+ILRR = 1 AT+ILRR ? AT+ILRR = ? (It is used to report the local DCE-DTE rate in control format in any incoming or outgoing call before CONNECT msg)

Ok ok

+ILRR:<mode> +ILRR: <list of mode> <mode>; 0; disable reporting 1; enable reporting

4 AT+CCFC = <reasons>, <mode>, [<number>]

ok when ,mode> = 2 +CCFC : <status>, <class>

or +CME ERROR : <err> +CCFC : (list of supported rea-sons) <reasons> : 0; unconditions





1; mobile busy 2; no reply 3; not reachable 4; all call forward-ing 5; all conditional call forwarding <mode>: 0; disable 1; enable 2; query status 3; registration 4; erase <number>: Telephone number to call forward to <class>: Is the sum of integ-ers each representation a class of informa-tion 1; VOICE 2; DATA 3; FAX <status>: 0; not active 1; active

5 AT +CCWA ? AT +CCWA=? (it is used to set call waiting supplementary service

OK when <mode>=1 +CCWA:<status>, <class> Or CME Error <err> +CCWA :<n> +CCWA :(list of <n>s) <n>:(set/shows) the result code presentation status O; disable 1 ;enable 2;querry status <mode>:(when modes parameter is not given ,n/w is not interro-gated) O; disable 1 ;enable 2;querry status





<class>: 1;VOICE 2;DATA 3;FAX <status> :0;not active 1;active

6 AT +CLIP=[<n>] AT+CLIP? AT +CLIP=? (It is used to set & re-quest the status of the calling line identification presentation service)

OK +CLIP=<N>,<M> +CLIP:(list of supported <N>s) <m>:(parameter shows the sub-scriber CLIP services ) 0;CLIP not provisional 1;CLIP provisional 2; unknown <number>:storing type phone no. of format specified by <type> <type>:type of address octet in integer format

7 AT+CLIR=[<N>] AT+CLIR? AT+CLIR=? (It is used to set &request the set of call-ing line identification restriction service)

OK +CLIR :<N>,<M> +CLIR:(List of supported <n>s) <n> :parameter sets the adjust-ment for outgoing calls O; presentation indicator is used according to the subscription of CLIR services 1;CLIR invocation 2;CLIR;suppression <m> :(parameter shows the sub-scriber CLIR service status in the n\w O;CLIR is not provisional 1;CLIR provisional in perma-nent mode 2;unknown 3;CLIR temporary mode presen-tation restricted 4;CLIR temporary presentation allowed

8 AT+COLP=[<N>] AT+COLP=? AT+COLP=? (It is used to receive the set of calling line out-going presentation ser-vice)

OK +COLP:<N>,<M> +COLP:(List of supported <n>s) <n>: parameter sets the adjust-ment for outgoing calls O; presentation indicator is used according to the subscription of CLR services 1;COLP invocation 2;COLPsuppresion





<m>:(parameters show the sub-scriber colp service status in the n/w) O;COLP not provisional 1;COLP provisional in perma-nent mode 2;unknown 3;COLP temporary mode pres-entation restricted 4;COLP temporary mode pres-entation allowed

9 AT+CPBS=<SM> AT+CPBS=? AT+CPBS=? (It is used to set &request the status of the connected line identi-fication &presentation)

OK +pbs :storage >[<used >,<total>] +pbs:(list of supported <storag-es) <storage>:”sm”; SIM abbr. dial-ing phonebook “FD”;SIM fixed dialing phone-book “on”; sim own me phone book <used >: integer type value indi-cator indicating the no. of used location in selected memory <total>: Integer type value indi-cating the nos. of locations in selected memory

10 AT+CPBR=<index1>, [<index2>] AT+CPBR=? (Command is used to read a special entry or range of entries from the phonebook memory sto-rage)

+CPBR: <in-dex1>,<no.>,<type>, <text>,<CR>,<LF> +CPBR: <index2>,< no.>,<type>, <text> or CME error: <err> +CPBR: (list of supported <in-dex>) <nlength>,<+length> or CME error: <err> <index1>,<index2>,<index>; Integer type value in the range of location no. of phonebook memory. <number>: string type no. of format <type> <type>: Type of address octet in integer format. <text>: string type field of max. length <+length>,charactervset as specified by command selects TECH set+CS. <nlength>: Integer type value





indicating the max. length of field <number>. <+length>: Integer type value indicating the max. length of field <text>.

11 AT+CPBF=? AT+CPBF (Command is used to find a phone book entry using a search string)

Error <n>: 0; disable 1; enable <index1>,<index2>: integer type value in the range at location of the phonebook

12 AT+CPBW=<index>,<no.>,<type> AT+CPBW=? (Command is used to write a phonebook entry to a specified place in the phonebook memory storage)

OK +CPBW: <index>, <nlength>, <type>, <text>, <tlength> Define Values: <index>: integer type value in-dicating the range of location of no. of phonebook <nlength>: integer type value indicating the max. length of the field <type>: type of address octet in integer format <text>: string type field of max. length <tlength>: integer type value indicating the max length of the <text>

CONCLUSION:





Date: PRACTICAL # 5

AIM: To study call flow control commands APPARATUS: GSM trainer, RS 232 Cable, windows software, SIM card, computer terminal THEORY: The typical signal flow sequence covers the following area:

o Location updating o Mobile call origination o Mobile call termination

They also include authentication and ciphering and inter MSC call hand off. Location Updating: As users move about within and outside their home service area, the home system must know the locations of all active mobile stations in real time in order to deliver incoming calls. The location updating feature is invoked when can active MS User mover from one location area to another or when MS tries to access in the n/w and it is not already registered in the serving VLR for its present location. Local areas generally consists of multiples, continuous cells and are identified by location area iden-tifies (LAI). In GSM, the MS continuously monitors the transmission from the surrounding base sta-tion. When it determines that, it has moved to new location area, it initiates signaling sequence, which assumes the monitoring is now done by a different BSS, MSC and VLR.





Location updating sequence 1. The MS sends a location update requires to the new VLR via the BSS and MSC. 2. The VLR sends a location update message to HLR serving MSC, which includes the address

of VLR and the IMSI of Smithies updating of HLR is not required if the new LA is served by same VLR as the LA

3. The service and the security related data for the ms is downloaded to the new VLR. 4. The MS is sent an acknowledgement of successful location update. 5. The HLR requests the old VLR to delete data related to relocate MS.

Mobile Call Origination:

1. Initially user enter the called no& press the send key, MS establishes a signaling connection to the BSS on a radio channel. This may involve authentication and ciphering. Once this has been established the call setup procedure will take place according to sequence shown.

2. The MS sends dialed number indication service to the MSC 3. The MSC checks from the VLR if the MS is allowed the requested service if so MSC asks the

BSS to allocate necessary resources for the call 4. If the call is allowed MSC routs the call to GMSC 5. The GMSC routs call to local exchange of called user 6. The LE alerts the call terminal 7. Answer back from called back to MS through serving MSC which also completes speech

path to MS





Mobile Call Termination: A typical sequence for call originating in the PSTTN and terminating at an MS in a GSM network.

1. The PSTN user dials MSISDN of called user in GSM. 2. The LE routes the call to GMSC of called GSM user. 3. The GSM uses a dialed MSISDN to determine the servicing HLR for the GSM user and inter-

rogates it to obtain required routing no. 4. The HLR requests the current serving VLR for the called MS for a MSRN so that call can be

voted to the correct MSC. 5. The VLR passes the MSRN to HLR 6. HLR passes MSRN to GMSC 7. Using MSRN GMSC routes call to the serving MSC. 8. The MSC interrogates the VLR for current location area identity for the MS. 9. The VLR provides the current LAI for the MS. 10. The MSC pages MS via the appropriate BSS. The MS responds to the page and setup the ne-

cessary signaling links. 11. When the BSS has established the necessary radio links MSC is informed and call is deli-

vered to MS. 12. When MS answers the call connection is completed to the calling PSTN user.





Authentication and Encryption: The authentication and ciphering function in GSM are closely linked and are performed as a single procedure between MS and n/w the security procedure in GSM is based on so-called Private Key mechanism, which requires that a secret key be allocated and programmed into each mobile station. An authentication algorithm and an encryption algorithm are also programmed into MS at the time of service provisioning the relevant call flows are as shown.

1. At terminal location update VLR sends IMSI to HLR. 2. HLR returns security triplet (RAND, SRES, KC) to the VLR. 3. For authentication and ciphering the VLR sends RAND to the MS. 4. Using stored A3 algorithm and secret key Ki stered in the SIM and RAnd provided by the

VLR, the MS calculates SRES and returns it to the VLR using the A8 algorithm and Ki the MS also calculates the cipher key KC.

5. If the SRES returned MS matches the stored in SREC in the VLR, the VLR sends cipher key KC to the BTS, which uses KC for ciphering radio path. The MC uses its KC to cipher radio path using encryption algorithm AS.





Inter MSC Handoff: Cellular system must be able to provide the capability to handoff calls in progress from channel

to another. Handoff calls from one channel to another may be invoked for one of the following rea-sons:

• To avoid dropped calls when a subscriber crosses the boundary of one cell and moves into a neighboring cell.

• To improve the global interference levels. • To improve load balancing between adjacent cells.

The main criterion for all handoff to avoid dropped calls is the quality of transmission for the on-

going connection both uplink and downlink TX quality corresponds to each neighboring cell to which MS could potentially be handed over .Handoffs for traffic and balancing are det by BSC and MSC based information on congestion in various cells under their controls such handoffs represent top-down decisions and may have involved a no. of MSS and cells within system.





The TX performance measures that can be used for handoff decisions of the two types include BER. In GSM the MS takes measurement of received transmission quality on channels within serv-ing cell, as well as on channels in neighboring cells which are then reported to the serving BSC for handoff decisions. The handoffs may be inter MSC handoff is as shown.

1. BSC A informs MSC A that MS needs handover from BTS A to BTS B. 2. MSC A informs MSC B that a handover from BTS B is underway. 3. MSC A commands BSCA/BTSA to proceed with handover to BTS B. 4. BTS A commands MS to change to a specific channel on BTS B 5. MS informs BTS B that it is on specific channels on DTS B. 6. BTS B informs BSCA/MSCA that handover is complete. 7. MSC B informs MSC A that no. is complete 8. MSC A continuously maintains control of call routing and connection.





OBSERVATION TABLE: SR. NO.

COMMANDS AND

INTERPRETATION

POSSIBLE RESPONSE

ACTUAL RESPONSE

1 Mobile originated call ATD 9879549606 (Command is used to es-tablish a voice call)

OK; If call is established BUSY; If called party is in another call NO ANSWER; If called party doesn’t accept a call NO CARRIER; If there are prob-lems to establish a call Defined values: <number>: Telephone number to dial

2 AT + VTS = ? List of supported <tone>s Defined values: <tone>: A single ASCII character, in the set 0-9, #, *, A-D.

3 AT + VTD = <4> AT + VTD = ? AT + VTD = ? AT + VTD = 5 AT + VTD ?

OK +VTD:<n>

List of supported <n>s Defined values: <n>: Tone of duration <n>* 100 ms

4 ATDL; Command is used to redi-al the last number)

CONNECT<speed>; If call is es-tablished OK ; If voice call is established BUSY; If called party is in another call NO ANSWER ; If called party doesn’t accept a call NO CARRIER ; If there are prob-lems to establish a call <speed> ; link baud rate between the modem and network.

5 ATA (Command is used to ac-cept an incoming call)

OK ; If incoming call is a voice call CONNECT<speed>; If incoming call is a data call <speed> : see ATD command

6 ATSO = 000 ATSO ? (The SO parameter con-trols the automatic ans-wering of an incoming call) ATSO = 005 ATSO ?

OK <n>

<n>; Automatic answer after <n> rings. A value of 0 disables auto answering.

7 ATH (Command is used to

OK or error





terminate a call) 8 AT + CBST = [<speed>,

0, [<ce>]] AT + CBST ? AT + CBST = ? AT + CBST = 7,0,1 (Command is used to se-lect the barrier service type and transparent mode for data connec-tion) AT + CBST = 14,0,1 AT + CBST = ?

OK + CBST:<speed>, 0, <ce> + CBST:(list of supported <speed>s, o, list of supported <ce>s) <speed>: 0;Auto bauding (Auto-matic selection of the speed) 1 ; 300 bps (V.21) 2 ; 1200 bps (V.22) 4 ; 2400 bps (V.22 bis) 6 ; 4800 bps (V.32) 7 ; 9600 bps (V.32) 8 ; specific 12 ; 9600 bps (V.34) 14 ; 14400 bps(V.34) 65 ; 300 bps (V.110) 66 ; 1200 bps (V.110) 68 ; 2400 bps (V.110) 70 ; 4800 bps (V.110) 71 ; 9600 bps (V.110) 75 ; 14400 bps (V.110) <ce> : 0 ; transparent 1 ; non-transparent 2 ; transparent preferred 3 ; non-transparent preferred

CONCLUSION:





Date:

PRACTICAL # 6

AIM: To study message handling commands. APPARATUS:

GSM trainer, RS 232 cable, Windows software, SIM card, Computer terminal THEORY: There are two basic types of services offered through GSM:

1) Telephony (Teleservices) 2) Data (Bearer services)

Telephony services are mainly voice services that provide subscribers with the complete capability (including necessary terminal equipment) to communicate with other subscribers. Data services pro-vide the capacity necessary to transmit the appropriate data signals between two access points creat-ing an interface to the network. In addition to normal telephony and emergency calling, the following subscriber services are supported by the GSM: Dual Tone Multi-Frequency (DTMF): DTMF is a tone signaling scheme often used for various control purposes via the telephone network such as remote control or an answering machine. GSM supports full-originating DTMF. Facimile Group III: GSM supports CCITT group 3 facimile. As standard Fax machines are designed to be connected to the telephone, using analog signals, a special Fax converter connected to the exchange is used in the GSM system. This enables a GSM connected fax to communicate with any analog fax in the net-work. Short Message Service: A convenient facility of the GSM network is the SMS. A message consisting of 160 alphanumeric characters (max) can be sent to or from a mobile station. This service can be viewed as an advanced form of alphanumeric paging with a number of advantages. If the subscriber mobile is powered off or has left the coverage area, the message is stared and offered back to the subscriber when the mo-bile number is powered ON or has re-entered the coverage area of the network. This function ensures that the message will be received. Cell Broadcast: A variation of the SMS services is the cell broadcast facility. A message of a maximum 93 characters can be broadcast to all mobile subscribers in a certain geographic area. Typical applications include traffic congestion warnings and reports on accidents. Voice Mail: This service is actually an answering machine within the network, which is controlled by the sub-scriber. Calls can be forwarded to the subscriber’s voice-mail box and the subscriber checks for mes-sages via personal security code.





Fax Mail: With this service the subscriber can receive fax messages at any fax machine. The message are stored in a service centre from which they can be retrieved by the subscriber via a personal security code to the desired fax number. OBSERVATION TABLE:

SR. NO.

COMMANDS AND

INTERPRETATION

POSSIBLE RESPONSE

ACTUAL RESPONSE

1 AT + CSCA=<SCA>,[;<tosca>] AT + CSCA=”919825001002”,145 AT + CSCA? AT + CSCA =? Command is used to set a service centre address. Mobile originated Mes-sage are transmitted through s.c.

OK

+CSCA:<sca>,<tosca> OK

<sca>:GSM 04.11 RP service centre address. Address value field instring format <tosca>:GSM 04.11 RP service centre address. Type of address octet in int format

2 AT + CMGL = ALL + CMGL:<index>,<stat>, <oa/da>,[<scts>], [<tooa/toda>],<length>, <CR><LF><data> [<CR><LF>] or + CMS ERROR Defined values: <tooa>:GSM 04.11 TP origina-tion address <length>:Integer type value indi-cating the length of message body <data> in characters <data>:GSM 03.40 TP User-Data in text mode responses





AT + CMGL =? (It is used to read se-lected messages from SIM card storage)

+CMGL:(list of supported <stat>s) <stat>:string type indicates the status of msg in memory “REC UNREAD”: Received un-read msg (i.e.new msg) “REC READ”: Received read message “STO UNSENT”: stored unsent message “STO SENT”: Stored sent mes-sage “ALL”: All messages <index>:Integer type:value in the range of location nos. supported by the associated memory <oa>:GSM 03.40 TP originating Address value field in string for-mat <da>:GSM 03.40 TP destination address <scts>:GSM 03.40 TP service centre Time stamp in time string format <toda>:GSM 04.11 TP destination address type of address octet in int format

3 AT + CMGR=? AT+CMGR=[<index>]15 Command is used to read one message from the SIM card storage.

OK If SMS delivers. +CMGR:<stat>,<oa>, <scts>, [<tooa>,<fo>,<pid>,<dcs>, <sca>,<tosca>,<length>, <CR>,<LF>,<data> If SMS submits: +CMGR: <stat>,<da>, [<to-da>,<fo>,<pid>,<dcs>, [<VP>]<sca>,<tosca>, <length>]<CR><LF>, <data> Defined values: <fo>:first octet of GSM 03.40 SMS deliver or SMS submit <pid>:GSM 03.40 TP protocol Identifier in integer format (de-fault 0) <dcs>:GSM 03.38 SMS data cod-ing scheme (0 default) <VP>: GSM 03.40 TP validity period in integer(167 default) or time string format <length>:Integer value indicating





length of message body <data> in characters. <data>:GSM 03.40 TP user data in text mode responses

4 AT + CMGS=<da>,[<toda>]<CR> AT + CMGS=“9898677388” AT + CMGS =? Command is used to send a msg to a service centre.

+CMGS:<mv>

OK <mv>:GSM 03.40 TP message reference in integer format

5 AT + CMSS=<index>,[<da>[<toda>]] AT + CMSS=19,9898677388 AT + CMSS=? Command is used to send a message from SIM and storage to the service centre

+ CMSS:<mv>

OK <index>:integer type, value in the range of location nos.supported by SIM memory. <da>:TP destination address, string format <toda>:GSM 04.11 TP destination address type of address octet in integer format(when 1st character of <da> is +(IRA43) default is 145 else 129)

6 AT+CMGW=<oa\da>,[<tooa>,<toda>, [,<start>]<CR>txt is en-tered <ctrl z| ESC> AT + CMGW=? Command is used to write a msg to the SIM card storage

+ CMGW:<index>

OK <oa>:GSM 03.40 TP originating address value field in string for-mat. <da>:GSM 03.40 TP destination address <toda>:GSM 04.11 TP destination address type of address octet in int format

7 AT + CMGD=<index> AT + CMGD=16 AT + CMGD=? Command is used to de-lete a msg from SIM card storage

OK

OK <index>: integer; value in the range of location nos. supported by SIM memory

CONCLUSION:





Date:

PRACTICAL # 7

AIM: To study the message setting commands. APPARATUS:

• GSM Trainer Kit • RS-232 Cable • PC with Windows • SIM Card

OBSERVATION TABLE: Sr. No.

Command And Interpre-tation


(1) AT+CSMS=<service>,<mt1>, <mt0>,<pin> AT+CSMS=0 AT+CSMS? AT+CSMS=? (command is used to select messaging services. It also shows supported services, where <mt> stands for mobile terminated msgs,<mo> mobile origi-nated & <bm> broadcast type messages )

OK +CSMS:<service>,<mt1>,<mt0>,<bm> +CSMS:(list of supported <service>s) Defined Values: <service> : 0,GSM 3.40 & 3.41(GSM stands for SMS,cell broadcast) 1….127 Reserved 128… Manufacturer specific <mt>,<mo>,<bm>:0;type not supported 1;type supported

(2) AT+CMPS=<mem1>[,<mem2>[, [,<mem3>]]AT+CMPS= “SM”, “SM”, “SM” AT+CMPS?

+CMPS:<used1>,<total1>,<used2>,<total2> ,<used3>,<total3> or Error +CMPS: <mem1>,<used1>,<total1> <mem2>,<used2>,<total2> <mem3>,<used3>,<total3> OR





AT+CMPS=? (command is used To select memory storage that will be used for Reading<mem1>& Writing<mem2> Short msgs to & for writ-ing broadcast<mem3>to:)

Error +CMPS:(list of sup-ported<mem>s), (list of sup-ported <mem3>s) Defined Values: <mem1>: String type; memo-ry from which messages are read & deleted. “SM”: sim message storage “BM”: broadcast message storage <mem2>: string type; memo-ry to which writing & sending operations are made. <mem3>: string type; memo-ry to which receive SMS are preferred to be stored. <total1>: integer type; total no. of msg location in <mem1>. <total2>: integer type; total no. of msg location in <mem2>. <total3>: integer type; total no. of msg location in <mem3>. <used1>: integer type; no. of msgs currently in <mem1>. <used2>: integer type; no. of msgs currently in <mem3>.

(3) AT+CMGF=<mode> AT+CMGF=0 AT+CMGF? AT+CMGF=? (command is used to select format for incoming & outgoing messages.)

OK +CMGF: <mode> +CMGF: (list of sup-ported <mode>s) Defined Values: <mode>: 0; PDU mode 1; text mode





(4) AT+CSMP=[<F0>[,<VP> [,<PID>[,<DCS>]]]] AT+CSMP=17,167,0,240 AT+CSMP? AT+CSMP=? Command is used to set additional parameter for text mode msgs.

OK +CSMP:<F0>,<VP>,<PID>,<DCS> OK Defined values: <f0>:first octet of gsm03.40 sms Deliver,sms submit in-teger format <vp>:gsm03.40 tp-validity period either in Integer format or in time string format <pid>:gsm03.40 tp-protocol identifier in integer for-mat <dcs>:gsm03.38 sms data coding scheme in integer format

(5) AT + CSDH = [<SHOW>] AT + CSDH = 0 AT + CSDH ? AT + CSDH = ? (command controls wheth-er detailed header informa-tion is shown in text mode results )

Ok +CSDH : LSHOW> +CSDH:(list of supported <SHOWS>s) <SHOW>: o: Do not show header values defined in commands tcsca & tcsmp(<sca>,<tosca>,<fo> <vp>,<pid>&<dcs>)

(6) AT+CSCS=[<chset>] AT+CSCS=GSM AT+CSCS? AT+CSCS=? Command is used to set & request the implemented chararter set . Incoming characters are converted to the current used set .

Ok +CSCS:<chset> +CSCS:( list of supported <chset>s) <chset> : “GSM”GSM default alphabet (GSM 03.38) “PCC437”PC character set Code page 437.





(7) AT+CNMI=[<mode>[,<mt>[,<bm> [,<ds>[,<bfr>]]]]] AT+CNMI? AT+CNMI=2,0,1,1,1 (used to select the proce-dure , how receiving of msg from the n/w is indi-cated to the TE is active)

+CNMI : (list of supported <mode>s, <bm> <bm>s,<ds>s,<bfr>s) +CNMI : <mode>,<mt>,<bm>,<ds>,<bfr> +CMS error : <err> Defined values : <mode> o:Buffer unsolicited result codes in the TA. If TA result code buffer is full , indications can be buf-fered in someother places or the oldest indications may be discarded & replaced with the new received indications . 1; discard indication and re-ject new received msg . unso-licited result codes when TATE links is reserved (eg in online data mode )otherwise forward them directly to the TE . 2:buffer unsolicited result codes in the TA when TATE links is reserved (eg inonline data mode ) and flush them to the TE after the reservation otherwise forward directly to TE. 3: forward unsolicited result code directly to the TETATE links specifin in band tech-nique used embed result codes and data when TA is in online data mode. <mt>: o : no sms deliever in-dications are rooted to the TE . 1: indications of sms deliver is routed to the TE using un-solicated result code. : TCMIT:<mem>,<index> 2:sms deliver (except class 2 )msg are rooted directly to the TE unsolicated result code . PDU mode enclosed : +CMT





:[<alpha>,<length><CR><LF><pdu> Text mode enabled (about parameters in italics , refers command show text mode parameters + CSDA ): +CMT :<oa>,[<alpha>],<scts>[,tooa>, <fo>,<pid>,<dcs>,<sca>,<tosca>,<length>] <cr><data> Class 2 messge result in indi-cations as defined in <mt>=1 3: class3 SMS-DELIVERS are routed directly to the TE using unsolicited result codes defined in <mt>=2. Messages ofted to the TE us-ing other class result in indi-cations as defined in <mt>=1 <bm>:o: No CBM indications of new CBM are routed to the TE 1:Indications of new CBM is routed to the TE using un-solicited result code : +CBMI : <mem>,<index> 2: New CBMS are routed directly to the TE using unso-licited result code : -PDU mode enabled: +CBM : <lenght><CR><LF><pdu> -Text mode enabled . +CBM:<SN>,<mid>,<dcs>,<page>,<CR>, <LF>,<data> 3:class 3 CBMS are routed directly to TEusing unsoli-cited result codes defined in <bm>=2 msgs of other classes result in indications as defined in<bm>=1. <ds> :o:No sms status reports are routed to the TE . 1: SMS status reports are routed to the TE using unsoli-cited result code . -PDU mode enabled .





+CDS: <fo>,<mr>,[<ra>],[<tora>],<sctc>, <dt>,<st>. <bfr> : o: TA buffer of unso-licited result codes defined within this comm. & is flushed to the TE when <mode>1….3 is entered . (ok response shall be given be-fore flushing the codes ). 1: TA buffer of unsolicited result codes defined within this command is cleared when <mode>1…3 is entered .

(8 ) AT+CCSB=[mode] <mids><dcss> AT+CSCB =”0,1,5,320-478,922” AT+CSCB? AT+CSCB=? Command is used to set parameters of how broad-cast message one to be re-ceived .

OK OK +CSCB:<modes>,<mids>,<dcss> +CSCB: (list of supported <mode>s) Defined values : <modes>: o : message types specified <mids>and <dcss> are accepted 1 ; message types specified in <mids> & <dcss>are not Accepted . <mids> : string type ; all dif-ferent possiblep Combinations of BM msg . <dcss> : string type all differ-ent combinations of CBM data coding scheme .

CONCLUSION:





Date:

PRACTICAL # 8 AIM: To study various PN Codes in CDMA

(A) Barker code (B) MLS code (C) Gold code

APPARATUS: DSSS Trainer kit, connecting wires, LA2124 logic analyzer THEORY: PN SEQUENCE: A Pseudorandom noise (PN) sequence is a sequence of binary nos. eg + 1. Which ap-pears to be random but it is in fact perfectly determination. The sequence appears to be random in the sense that the binary values & groups or runs of the same binary value occur in the sequence in the same proportion. They would if the sequence were being generated based on a fair “coin tossing” experiment. In the experiment, A software or hardware de-vice designed to produce a PN seq. is called PN generator or PN sequence. These are known se-quences that exhibit the properties of characteristic of random sequence. They can be used to logical-ly isolate users on the same frequency channel. They can also be used to perform scrambling as well as spreading and despread to use PN sequences were deterministic, and then everybody could access the channel. If the code sequence were truly random on the other hand no one including the intended receiver would be able to access the channel. Thus using a pseudorandom sequence makes the signal look like random noise to everybody except to the transmitter & the intended receiver. PN SEQUENCE GENERATION: A PN generator is typically made of N cascaded feedback flip-flop ckts and a special-ly selected feedback arrangement as shown in fig. The flip-flop ckt when used in this way are called a shift register. Since each clock pulse applied to the flip-flop to be shifted to right. The feedback connections provide the feedback connections input to the left most f/fs, with N binary stages the larges no of different patterns the shift reg can have is 2^N. The all binary zero state, however is not allowed because it would cause all remaining states of the shift register and its outputs to be binary ones provided the no. of f/fs input to the module to adder is even For eg, starting with the register in state 001 as shown, the next 7 states are 100,010,101,110,111,011 & then 0010 again & the states continue to repeat. The output taken from the rightmost flip-flop 1001011 which repeats with the 3 stage shift register shown, the period is 23-1 or 7. The flip-flops that should be tapped 2 adder are determined by an advanced algebra method that has identified cer-tain binary polynomial called primitive irreducible or infactorable polynomials. Such polynomials





are used to specify the feedback taps. For eg 1S-95 specifies the in phase PN generator shall be built based on the characteristic polynomial

P(X)=X15+X13+X9+X8+X7+X5+1 Picture a 15 stage shift register with the right most stage numbered of the successive stages 1,2,3,….14 then the exponents less than 15. 15 in the above equation tells us that stages 0,5,7,8,9,13 should be tapped and summed in a module 2 adder. The output of a adder 2 is then input to the leftmost stage. The shift register PN sequence ge-nerator is shown below. PROPERTIES OF PN SEQUENCE: PN signals are deterministic signals. They can be shown to have the following three proper-ties.

(a) Balance Property: The no. of zeros & ones of a PN code are different only by one. (b) Run Property: The no. of times the ones & zeros repeat in or runs appear in the same propor-

tion they would if the sequence were actually generated by a coin tossing experiment. For an N bit code there would be N zeroes (or ones) runs. Half of these runs would be of length one.

CORRELATION PROPERTY: The correlation value of two N-bit sequence can be obtained by counting the no of similar Ns & dissimilar Nf bits 7& inserting them into the following equeations:- P=PN+(NS.ND) Types of PN Sequences in CDMA:

IS-GS uses two PN generators to spread the signal power uniformly over the physical band-width of about 125MHZ. The PN spreading on the reverse link also provides nearorthgonality of & hence, minimal interferences between signals from each mobile This allows reuse of the band of fre-quencies which is a major advantage of CDMA.

In IS-G5, two types of Max. length PN sequences of PN codes are used. The short PN code and long PN code.





Short Code: The short PN code is generated by a 15 stage linear shift registers. Therefore, the max. length of the short PN code is: L = 2N -1 = 215 – 1 = 32768 – 1 = 32767 By, implement an extra chip is inserted at end of the sequence yielding a sequence of length L=32768 chips. The short PN code runs at a speed of 1223,800 chips per second. This yields a repe-tition cycle of 32768/1228800=26.67ms. Long Code: The PN chips from the long code are used to provide several randomizing functions in the 1s-g5 system. These include providing chips. For message scrambling on the forward and reverse links, for identifying mobiles & access channels on reverse links by using unique offsets for each entity & for randomizing the location of the power control bits on the forward traffic channels. The long PN code is generated in a 42 stage linear effect. This yields a repetition cycle of 4.4x1012/11228800=41.42 days.

The long PN code is generated in a 42-stage linear shift register generator with the O/P of 42nd stages. I/P into the 1st stage & modulo-2 offered with the O/P of stages 1,2,3,5,7,10,16,17,18,19,21,22,25,26,27,31,33,&35.

CALCULATIONS:

(1) Chip Rate :

(a) 1 MHZ :

(b) 2 MHZ :

(c) 5 MHZ :





(2) Processing Gain:

(a) Barker Code :

(b) MLS Codes :

(c) Gold Code :

(3) Code Selection: (a) Barker Code :

(b) MLS Codes :

(c) Gold Code :

(4) Polynomial for Gain G1:

(a) For Barker Code :

(b) For MLS Code :

(c) For Gold Code :





(5) Polynomial for Gain G2: (a) For Barker Code :

(b) For MLS Code :

(c) For Gold Code :

(6) Offset Carrier Frequency:

(7) Maximum Signal Gain:

(8) Noise Gain:

(9) REG 18 (bit 7,bit 6,bit 5,bit 4,bit 3,bit 2,bit 1,bit 0) :-





(10) REG 19 (bit 7,bit 6,bit 5,bit 4,bit 3,bit 2,bit 1,bit 0) :-





CODE GENERATION:- (a) For MLS Code:

(1) G1 = 1+X2+X3

(2) G2 = 1+X2+X4 (b) For Gold Code:

(1) G1 = 1+x+x2 & G2 = 1+x2 (2) G1 = 1+x+x2 & G2 = 1+x+x4





(G1) (+) (G2)

(1) (2) O/P (1) (2) (3) (4)

1 1 0 1 1 1 1

0 1 0 0 1 1 1

1 0 0 1 0 1 1

1 1 1 0 1 0 1

0 1 1 1 0 1 0

1 0 0 1 1 0 1

1 1 1 0 1 1 0

0 1 0 0 0 1 1

1 0 0 1 0 0 1

1 1 1 0 1 0 0

0 1 0 0 0 1 0

1 0 1 0 0 0 1

1 1 0 1 0 0 0

0 1 1 1 1 0 0

1 0 0 1 1 1 0

1 1 0 1 1 1 1

CONCLUSION:





Date:

PRACTICAL # 9

AIM: To generate DSSS modulated signal Modulation using internal generation of 2047 bit of PN sequence as modulator and demodulator carrier. APPARATUS: CDMA trainer kit, pc, CRO, connecting wires, probes etc. THEORY:

Direct sequence is spread spectrum technique in which the bandwidth of the signal is in-

creased by artificially increasing the bit rate data. This is done by breaking each bit into a number of sub-bits called “chips”. E.G. if this one s 10, each bit in original signal would be divided into 10 sep-arate bits or chips. This results in an increase in data rate by 10 (b/w) by 107.

The signal is divided into smaller bits by means of a PN sequence. Can be done by using a two i/p EX-OR gate; where one i/p is low speed. Data; & other i/p is a high speed PN sequence.

The data signal has a narrow power spectrum. The high speed PN code, in comparison, has a wider power spectrum. The result is that the composite signal has same transition rate as the PN se-quence (because of wideband power spectrum, but lower amplitude, as total energy is constant.)





To recover data from this another EX-OR is used where composite data c is applied to one i/p & an identical PN sequence as second i/p. the o/p y is original signal. It is important to note that the recovery process only works when the PN sequence is identical for both spreading & dispreading. One of the main advantages of spread spectrum signal is its tolerance to interference. The re-ceived signal is the original signal with very low amplitude noise spread across the entire bandwidth of spread signal. The original signal can be recovered. Hence, by band pass filtering. Since energy s conserved, the magnitude of the interference power is reduced considerably (proportionally) referred to as “Process low.” Therefore, all users other than the desired signal appear as noise, for k users. CDMA gain = Process gain - Process loss due to K users = 10 log (Bw/Rb) – 10 log k = 10 log (Bw / K.Rb)





CALCULATIONS: For Modulation: Reg 18 (Bit 7, 6 … Bit 0) bit 0 0 ; internal c/k 1 ; External c/k bit 1 0 ; 2’s complement 1 ; unsigned bit 3 & bit 2 00 ; BPSK 01 ; QPSK 10 ; 0QPSK bit 5 & bit 4 00 ; disabled 01 ; PRBS 10 ; internal generation of 2047 bit periodic Ps udorandow bit seq. as modulator input 10; unmodulated carrier bit 6 0 ; off 1 ; on bit 7 (interpalation to max. c / k rate) 0 ; off 1 ; on We used For BPSK; (1001 0010) b (g2)H Reg18 (g2)H Reg 19 (Bit 7,6 …….. 0) bit 0 0 ; o/p data is pushed to the next module. 1 ; o/p data is pulled by the next module bit 1 (input format) 0 ; 1 bit serial 1 ; 2 bit parallel bit 2 0 ; disabled shaping filter 1 ; enabled shaping filter bit 3 0 ; disabled (spectrum) spreading 1 ; enabled spectrum spreading For BPSK (0000 1100) (OC)H Reg 19 OCH

Inverter Q bit





For Demodulation: Reg 16 (bit 7, 6 ... 0) bit 0 0 ; internal C/K 1 ; External C/K bit 1 0 ; 2’s complement 1 ; unsigned bit 3 & bit 2 carrier freq loop gain

00 nominal 01 2 X 100p gain 10 4 X 100p gain 11 8 X 100p gain

bit 4 reserved always 0 bit 5 spectrum inversion 0 ; off 1; on bit 6 Reserved always 0 bit 7 freeze monitoring data 0 ; freeze the monitoring data prior to reading it 1 ; re enable the update Reg 17 (bit 3,2,1,0) bits 1 – 0 00 ; I / Q Parallel 01 ; I / Q Serial bits 3 – 2 00 ; BPSK 01 ; QPSK Reg 16 : 02 h (0000 0010) Reg 17 : 01 h (0000 0001)





For Modulation: Code Reg No.

Barker Code 11 bit

Barker Code 13 bit

MLS code G1 = 1+x2+x3

MLS G1 = 1+x2+x4

Gold G1=1+x+x2

G2=1+x2

Gold G1=1+x+x2 G2=1+x+x4

0 66 66 66 66 66 66 1 66 66 66 66 66 66 2 06 06 06 06 06 06 3 0B 0D 07 0F 03 0F 4 00 00 00 00 00 00 5 00 00 00 00 00 00 6 03 03 02 02 01 01 7 00 00 06 0A 03 03 8 00 00 00 00 00 00 9 00 00 00 00 00 00 10 00 00 00 00 02 09 11 00 00 00 00 00 00 12 00 00 00 00 00 00 13 00 00 00 00 00 00 14 00 00 00 00 00 00 15 00 00 00 00 00 00 16 FF FF FF FF FF FF 17 00 00 00 00 00 00 18 02 02 02 02 02 02 19 0C 0C 0C 0C 0C 0C





For Demodulation: Code Reg No.

Barker Code 11 bit

Barker Code 13 bit

MLS code G1 = 1+x2+x3

MLS G1 = 1+x2+x3

Gold G1=1+x+x2

G2=1+x2

Gold G1=1+x+x2 G2=1+x+x4

0 66 66 66 66 66 66 1 66 66 66 66 66 66 2 06 06 06 06 06 06 3 0B 0D 07 0F 03 0F 4 00 00 00 00 00 00 5 00 00 00 00 00 00 6 03 03 02 02 01 01 7 00 00 06 0A 03 03 8 00 00 00 00 00 00 9 00 00 00 00 00 00 10 00 00 00 00 02 09 11 00 00 00 00 00 00 12 00 00 00 00 00 00 13 00 00 00 00 00 00 14 00 00 00 00 00 00 15 00 00 00 00 00 00 16 02 02 02 02 02 02 17 01 01 01 01 01 01

CONCLUSION:





Date:

PRACTICAL # 10 AIM: To study various code modulation tech. QPSK, BPSK, OQPSK APPARATUS: CDMA trainer kit, PC, oscilloscope, connecting wires, probes. THEORY: There are different types of code modulation techniques employed to modulate the data to be retransmitted the basic QPSK, BPSK, OQPSK. Binary phase shift keying (BPSK): For Binary PSK (BPSK) S0 (t) = A.coswt represents binary “0” S1 (t) = A.cos(wt + π) represents binary “1” For M-ary PSK, M different phases are required, and every n (where M=2n) bits of the binary bit stream are coded as one signal that is transmitted as

A.sin(wt+θj) θj = 1, 2. . . .n

Binary phase shift keying (BPSK) demonstrates better performance than ASK & FSK. PSK can be expanded to an M-ary scheme, employing multiple phases and amplitudes as different stages. Filtering can be employed to avoid spectral spreading.





Quadrature Phase Shift Keying (QPSK):

If we defined four signals each with a phase shift differing by then we have quadrature phase shift keying. The QPSK transmitter system uses both the sine & cosine at carrier frequency to transmit two separate msg signals: SI(n) & SQ(n) referred as the inphase & quadrature signals. These are simply I & Q gain as function of n. Provided that a coherent receiver system is employed both I &Q signal can be recovered exactly allowing us to transmit twice the signal information at the same carrier frequency. The i/p binary bit stream {dk} dk = 0, 1, ….. arrives at modulator i/p at a rate 1/T bits/sec and is separated into two data streams dI and dQ containing odd and even respectively. dI (t) = d0, d2, d4 …… dQ (t) = d1, d3, d5 …… QPSK is effective two independent BPSK sys. (I & Q) & this exhibits same performance but twice the bandwidth efficiency. QPSK can be filtered using raised cosine filters to achieve excellent band suppression. Large envelope variations occur during phase transitions thus requiring linear amplifica-tion. Offset Quadrature Phase Shift Keying (OQPSK): If the two bit streams I & Q are offset by ½ bit interval, then the amplitude fluctuations are

minimized since the phase never changes by this modulation scheme , OQPSK is obtained from QPSK by delaying odd bit stream by half a bit interval with respect to the even bit stream. Thus

the range of phase transitions is (the possibility of a phase shift of is eliminated) & occurs twice as often, but with half the intensity of the QPSK. While amplitude fluctuations still oc-cur in transmitter & receiver. They have smaller magnitude. The bit error rates for QPSK & OQPSK are same as that for BPSK.

When an OQPSK signal undergoes band limiting the resulting inter-symbol interference

causes the envelope to drop slightly to the region of phase transition but since the phase transi-

tions of 180 have been avoided in OQPSK, the envelop will never get to zero as it does in QPSK. CALCULATIONS: BPSK: Modulator: Reg 18





Reg 19 Demodulator: Reg 16 Reg 17





QPSK: Modulator Reg 18 Reg 19 Demodulator: Reg 16 Reg 17





OQPSK: Modulator

Offset carrying frequency =

Given F sample clock = 32 kHz

= 16 kHz

So, offset carrier frequency = =

= (800000)h Reg 13 = (00)h Reg 14 = (00)h Reg 15 = (80)h Reg 18 Demodulator: Nominal centre carrier frequency

=

=

= (4194304)d

= (400000)h Reg 13 = (00)h Reg 14 = (00)h Reg 15 = (40)h For OQPSK (demodulator) values of Reg 16 & 17 are same as QPSK (demodulator).





Modulator: Reg no.

Mod tech. BPSK QPSK OQPSK

0 66 66 66

1 66 66 66

2 06 06 06

3 7F 7F 7F

4 00 00 00

5 00 00 00

6 02 02 02

7 41 41 41

8 00 00 00

9 00 00 00

10 00 00 00

11 00 00 00

12 00 00 00

13 00 00 00

14 00 00 00

15 00 00 80

16 FF FF FF

17 00 00 00

18 92 D6 DA

19 0C 0E 0E





Demodulator: Reg no.

Mod tech. BPSK QPSK OQPSK

0 66 66 66

1 66 66 66

2 06 06 06

3 7F 7F 7F

4 00 00 00

5 00 00 00

6 02 02 02

7 41 41 41

8 00 00 00

9 00 00 00

10 00 00 00

11 00 00 00

12 00 00 00

13 00 00 00

14 00 00 00

15 00 00 40

16 02 22 22

17 01 04 04

CONCLUSION:




Documents

Mobile Lab Manual