WLAN – Wireless Platform for Future Services

5ZNUV 2014;38;5-19

Iwona Dolińska, Antoni MasiukiewiczAkademia Finansów i Biznesu Vistula – Warszawa

WLAN – Wireless Platform for Future Services

Summary

Many wireless standards have been developed up till now; however, only two of them are com-monly used. The mobile telephony and WLAN networks dominate in the wireless services sector. The number of mobile network customers reaches billions and this number still increases. Are the present achievements a border for wireless technologies? During the last years it has become evident that wireless data rates are increasing over time. Another question remains open: will be there a need for data rates above 100 Mbit/s in future? Today already more than 50% of data transmission on mobile networks is the effect of the video streaming applications.

Key words: WLAN, WiFi, IEEE standard, QoS, 60 GHz.

JEL codes: O33

Introduction

Many wireless standards were developed up till now, however only two of them are commonly used. Mobile telephony and WLAN networks dominate in the wireless services sector. The number of mobile network customers reaches billions and this number still in-creases. WLAN networks have a different philosophy and they base on ISM (industrial, scientific, medical) bands, which are public free frequencies (Hiertz et all 2010). The fact that both mentioned systems are wireless and popular are the only similar features. Mobile telephony is the commercial standard, which uses dedicated frequency bands, which are only commercially available. The mobile operator could plan and manage its network as well as its clients. The WLAN networks have much more complicated nature. We could define a few types of 802.11 networks such as: networks with or without AP, mesh networks, in which the stations can communicate directly, administrated networks, high density networks and the small private and home networks. There are completely different rules in WLAN networks, than in mobile telephony. WLANs are a good example of totally chaotic and not administra-tive area. There are of course some well organised examples at enterprises or so called Hot Spots, but generally speaking WLAN is the area with no supervising or administration as long as the way of band utilization is lawful (the proper equipment is used as well as the power limit is not exceed and the centre frequency and channel width are compatible with standard requirements). It means that everybody can use this frequency range, anyone has the priority and no protection against other user is guaranteed. The number of WLAN users is difficult to establish, so the market potential is estimated rather on the base of chipset pro-duction and sells (Aruba White Paper 2012). These figures are quite impressive. The chipset shipment realisation and forecast for years 2007-2014 is presented in Fig. 1.

Zeszyty-naukowe-38_2014.indd 5 2014-12-17 11:38:09

WLAN – WIRELESS PLATFORM FOR FUTURE SERVICES6

Fig. 1WLAN chipset production and shipment forecast

Source: Aruba White Paper (2012).


IWONA DOLIŃSKA, ANTONI MASIUKIEWICZ 7

Presently the most popular standard is 802.11n (Cisco White Paper 2012), however the situation could change, because of two new standards 801.11ad (released in 2012) and 801.11ac (planned confirmation at the end of 2013) (Masiukiewicz 2013;Cisco White Paper 2012). The chipset selling per year reaches the level of billions pieces. There are a few 802.11 (WLAN) standards in use, such as 802.11 a/b/g/n/ac/ad and a lot of standard modi-fications e.g. 802.11e, which implements the mechanisms improving QoS parameters. The authors give a short overview of standard history, discuss the most important technical issues and the scope of services available in most popular standards nowadays.

Development of WLAN Wireless Standards

802.11, WLAN or WiFi (all these terms are used often as equivalent names of WLAN) start-ed its history in 1985, when the United States Federal Communications Commission opened several frequency bands for use without government license. The first IEEE 802.11 standard was defined in 1997. Then several new versions as well as amendments were subsequently developed (Hiertz 2010). The main parameters of 802.11 standards are presented in Table 1.

Table 1Basic parameters of IEEE 802.11 standards

Standard Frequency band[GHz]

Channel width[MHz] Antenna system Max. throughput3

[Mbits/s]

802.11a 5 20 SISO1 54802.11b 2,4 20 SISO 54802.11g 2,4 20 SISO 11802.11n 2,4 ; 5 20 ; 40 MIMO2 150802.11ac 5 20 ; 40; 80 ; 160 MIMO 867802.11ad 60 2160 SISO 4620

1 single input single output2 multiple input multiple output3 per single spatial streamSource: own preparation.

802.11b was the first standard version. It offered the maximal throughput of 11 Mbits/s in 2,4 GHz band. This band is susceptible to possible interferences from other devices using the same frequencies, especially Bluetooth. The 5 GHz band was implemented in 802.11a and subsequently in 802.11n and 802.11ac standards. Two newest solutions 802.11n and 802.11ac introduced some new techniques such as channel bonding, higher level of modula-tion and packet aggregation. Many improvements leads to higher and higher throughput.



Technical Issues

The 802.11n standard was quite revolutionary (Cisco White Paper 2012; IEEE 2009). There are a long list of the new solutions in both basic layers PHY and MAC. Some of the changes however are not supported in 802.11ac standard. The most important innovations in the 802.11n standard are as follows: - MIMO (multiple input multiple output) implementation – this solution offers two main

benefits. The SM (spatial multiplexing) splits up the data into pieces and sends each piece along parallel “spatial” channels in a fraction of the time that it would take to send the same data serially through single channel. The multipath transmissions increased uplink reliabil-ity. Due to multipath, an AP with four antennas receives four copies of a sender’s signal. Each copy is distorted in four different ways, so the probability that all copies are destruc-tively faded all at the same time is very low. Thus the MIMO equalizer within the receiver can gather all these copies, combine them, and as a result the greater reliability is achieved,

- channels bonding – allows to increase the channel width from 20 to 40 MHz. It results in doubling the throughput. The channel bonding is available for both 802.11n frequency bands 2.4 GHz and 5 GHz,

- aggregation - two aggregation techniques are used : the “intuitively” named A-MSDU and AMPDU, which can also be combined together, as in “A-MPDU of A-MSDU.” With aggregation, the data packets are packed together in a single unit, that is sent with one preamble and acknowledged in one transmission,

- others - new modulation schemes, which include the higher modulation level and coding rate, short guard interval (400 ns), mixed modulation, block ACK, three operating modes (HT-greenfield, non HT, HT mixed).The 802.11n standard could use two frequency bands the same like in other 802.11 prod-

ucts. Basic channels are approximately 20 MHz wide. Within the 2.4 GHz ISM frequency band transmitters use one of 11, 20 MHz channels (three of them are theoretically non-over-lapping: 1, 6,11). There are 12 non-overlapping 20 MHz channels in the 5 GHz UNII band.

The 802.11ac standard doesn’t introduce almost anything new (Aruba White Paper 2012; Netgear White Paper 2012). One could say, that this standard is the optimization of the 802.11n standard. There are some changes, but there are no new technologies. The 802.1ac standard increases the number of spatial streams to eight and allows the simultaneously com-munication of AP with eight different stations. On the other hand, it reduces the aggregation modes available in the 802.11n standard. The MIMO technology used in 802.11ac standard is called multi user (MU) technique, while the 802.11n MIMO is called single user (SU). The 802.11ac standard is practically an improved version of 802.11n standard. 802.11ac improves 802.11n on three different dimensions: - more channel bonding, increased from the maximum of 40 MHz in 802.11n up to 80 or

160 MHz,



- denser constellation (modulation levels), now using 256 quadrature amplitude modula-tion (QAM), comparing with 802.11n’s 64QAM,

- more multiple input, multiple output (MIMO) streams, the 802.11n stopped at four spa-tial streams, 802.11ac reaches eight.Channel bonding in 802.11ac base on simple principle. Adjacent 20 MHz sub-channels

are bonded into pairs to make 40 MHz channels, adjacent 40 MHz sub-channels are bonded into pairs to make 80 MHz channels, and adjacent 80 MHz sub-channels are bonded into pairs to make the optional 160 MHz channels

QoS in Wireless Transmissions

Ensuring an appropriate QoS level in WLAN is necessary, because of constantly increas-ing demand for streaming audio, video or multimedia transmission (Dolińska, Masiukiewicz 2012). On the other hand, providing the expected by users QoS level in wireless networks is a difficult problem. The quality of transmission parameters can originate from many fac-tors, like the value of the used frequency, the distance between access point and stations, the number of obstacles on the propagation path, etc. A significant impact on QoS has also the density of WLANs used on the same area. The Table 2 presents the most important pa-rameters determining the transmission quality. The parameters are grouped in accordance to the transmission channel elements, like transmitter, receiver, radio channel and network access management. The transmitters and receivers parameters are defined unambiguously by standards and other rules. But radio channel parameters are characterized by a high vari-ability in the time.

Table 2Factors determining QoS

Transmitter Transmit power, frequency, S/N ratio, standard version, throughput.

Radio channel The distance between stations, frequency, attenuation in the channel (weather conditions, terrain), multipath propagation, station mobility, within and inter channel interferences.

Receiver Sensitivity, noise level, standard version.Access management Login, transmission, retransmission, frame size, access maintain mechanisms,

standard version.

Source: Dolińska, Masiukiewicz (2012),

Transmission quality providing on the level demanded by the user is much more difficult in the wireless networks than in fixed networks.



Services in 802.11n and 802.11ac Standards

The first popular standards for wireless LAN (IEEE 802.11a and 802.11b) were designed primarily to fulfill the needs of a laptop PC in the home and office, and later to allow con-nectivity “on the road” in airports, hotels, Internet cafes, and shopping malls (Hiertz 2010). Their basic function was to provide an access to a wired broadband connection for Web browsing and email. Since the speed of the broadband connection was the limiting factor, a relatively low-speed wireless connection was sufficient – 802.11a provided up to 54 Mb/s at 5 GHz, and 802.11b up to 11 Mb/s at 2.4 GHz, both in unlicensed spectrum bands. To min-imize interference from other equipment, both used ways of spread-spectrum transmission and new modulation types such as OFDM and QAM. The high throughput (HT) is required for many applications now (Cisco white paper 2012). There are others transmission param-eters, which describe the QoS such as delay or jitter, but we discuss them when we have satisfactory throughput. The most critical application is multimedia transmission. Streaming video, even when compressed, consumes orders of magnitude more bandwidth than voice communication, email and web browsing. The introduction of different type smart-phones and tablets has started enormous increases in bandwidth demand, while consumption of streaming video-over-IP in the home for TV and movies have started significant increases in Internet traffic and demands for throughput and capacity. The wireless display usage so-lutions are competing with the cross-room cable replacement market that at present was the objective of ultra-wide band (UWB) and that will overlap with the 802.11ad planned for 60 GHz band. The 802.11ad standard intention is to replace the cables between set-top boxes, game consoles, PCs and TV. Most consumer electronics companies see 802.11ac and 802.11ad as the first sensible wireless technologies for video, especially uncompressed vid-eo. The throughput necessary for different type video transmission was compared in Table 3.

Table 3Throughput for different type video transmissions

Video type Parameters Throughput

uncompressed 720p, RGB, 1280x720p, 60Hz 1300 Mbit/s

uncompressed 1080i, RGB, 1920x1080p, 60 Hz 1500 Mbit/s

uncompressed 1080p, RGB, 1920x1080p, 60 Hz 3000 Mbit/s

lightly compressed Motion jpeg2000 150 Mbit/s

lightly compressed H.264 70-200 Mbit/s

compressed Blu-ray 50 Mbit/s

compressed HD MPEG2 20 Mbit/s

Source: Cisco White Paper (2012).



Besides video applications the HT could be also useful in the case of large file transfer.

60 GHZ WLAN New Prospects

The 60 GHz is very interesting band, because of large amount of free spectrum resources. In 2001, the Federal Communications Commission (FCC) leave a spare continuous block of 7 gigahertz (GHz) of spectrum between 57 and 64 GHz for wireless communications (Masiukiewicz 2013; WiFi Alliance 2013). This is much more spectrum, that is presently available in 2,4 and 5 GHz . The short range offers also benefit of frequency reuse. There are several attempts of targeting 60 GHz band such as: IEEE 802.15-3c, WirelessHD, ECMA-387, ISO/IEC 13156, NGmS, WiGig TM, 802.11ad.

Table 4New WLAN usage models

Category Application area

Wireless display Desktop storage and displayProjection to TV or projector in conference room or auditoriumIn-room gamingStreaming from camcorder to displayProfessional HDTV outside broadcast pickupHD streams over HDMI or DP using A/V PALs

HDTV distribution Video streaming around the homeIntra-large-vehicle applications (e.g. airplane, ferry)Wireless networking for officeRemote medical assistance

Quick upload/download Rapid file transfer/syncPicture-by-picture viewingAirplane docking (manifests, fuel, catering, etc.)Downloading movie content to mobile devicePolice surveillance data transfer

Backhaul Multi-media mesh backhaulPoint-to-point backhaul

Outdoor campus/auditorium Video demo / tele-presence in auditoriumPublic safety mesh (incident presence)

Manufacturing floor AutomationInstant Wireless Sync IP based P2P applications

Using I/O PALsKiosk sync and data exchange

Cordless Computing Combination of display using A/V PALs, sync and I/O PALsDistributed peripherals

Networking Using native Wig /802.11adWiFi session transfer

Source: Cisco White Paper (2012); WiFi Alliance (2013).



Presently 802.11ad is the only one specification with relatively high probability of commercial success due to the engagement of operators, equipment producers, IEEE and Wireless Gigabit Alliance. All parties give a strong support to this project and in 2013 try to consolidate all previous technology to deliver unique solution. Wi-Fi Alliance is develop-ing the WiGig CERTIFIED™ program to deliver interoperable products. The program is expected to begin testing in 2014, and certified products will bear the certification mark WiGig CERTIFIED.

60 GHz is not suitable for long range transmissions, because of very high attenuation due to frequency value itself as well as influence of some factors, which are not critical for lower frequencies. This frequency could be however very useful for short range communication, especially when the wide channel is important. Such situation occurs in home application for multimedia transmissions. The list of possible application is however much more longer. Today there are many new usage models such as: desktop storage and display, projection in conference rooms, in-room gaming, streaming from camcorder to display and others.

However, by the same time, new usage models with the need for higher throughput had been recognized: data sharing amongst connected devices in the home or small office and wireless printing as examples. The scope of new services planned for 802.11ac and espe-cially for 802.11ad standards is presented in Table 4.

An idea of kiosk data supplier is quite a new one. It makes sense, if the proper throughput could be guarantee (Fettweis 2011). This is possible, when the 60 GHz band will be applied and with the c.a. 10 Gbits/s data transfer. A wireless data kiosk could be a vendor or sell-ing machine that allows for ultra-fast download of large amounts of bulk data (see Fig. 2) to a user terminal. The user is situated in front of the machine at a distance of less than 1m and both the transmitter and receiver have a LOS (line of sight) connection. The customer could exploit with download data as soon as the process has been finished. So he could immediately watch video, play music or games. Still there are some limits concerning the available energy sources especially for mobile users. Very short time, typically less than 10 s. is necessary to

Fig. 2Wireless data kiosk

Source: Fettweis, Guderian, Krone (2011).



introduce the kiosk. With a data rate close to 10Gbits/s, the content of one DVD (4.7 GB) can be downloaded in less than 4 s (see Table 5), whereas several minutes or even hours would have to be spent, when relying on more conventional solutions such bas old 802.11a standard or 2.0 Bluetooth.

Table 5Download times for different data throughput rates

Throughput/Data volume 1 GB 5 GB

3 Mbits/s Bluetooth 2.0 44 min 27 s 3 h 42 min 13 s54 Mbits/s 802.11a 2 min 28 s 12 min 21 s10 Gbits/s (60 GHz) 0,8 s 4 s


Beamforming in 60 GHz

The 60 GHz band using allows extremely fast communication, but also presents the chal-lenge, that propagation loss is higher than in the 2.4 GHz and 5 GHz bands. Signals in the 60 GHz band are more susceptible to disruption from physical barriers (especially walls) than at lower frequencies. The IEEE 802.11ad specification addresses this challenge using

Fig. 3The application of beamforming in multimedia communication

Source: WiFi Alliance (2013).



adaptive beamforming (WiFi 2013), a technique that enables robust multi-gigabit communi-cations at distances greater than 10 meters. Beamforming uses directional antennas to reduce interference and focus a signal between two devices into a concentrated “beam”. Support for beamforming is defined within the PHY and MAC layers of the IEEE 802.11ad specifica-tion. During the beamforming process, two devices establish communication and then fine-tune their antenna settings to improve the quality of directional communication until there is enough capacity for the desired data transmission so this techniques enables the application of several spatially diverse streams.

Another key benefit of beamforming is that if an obstacle blocks the line of sight between two devices - if someone walks between them, what happens often if someone is playing any interactive game, the devices can quickly establish a new communications pathway , it can use beams that reflect off walls to maintain communication (see Fig. 3).

Home Area Network

The intelligent building with hundreds meters of cables and wires seems to be an ancient technology nowadays. The wireless Home Area Network (HAN) (Guillory 2012) is the subse-quent solution, which could be useful for a decade. Its main function consists in managing and

Fig. 4Multimedia home (or wireless home network area or domestic cloud)

Source: Guillory (2012).



delivering a large set of services, including the Internet, to the different rooms of the house. While at the beginning the wireless communication is strongly required by the interactive games, the main driver of the market is the growing number of different multimedia devices ( see Fig. 4). This assignment becomes complex as today the number of connected devices inside the home increases, and each of them requires higher throughput. For instance, a High Definition (HD) film stored on a Network Attached Storage (NAS) can be read on a laptop, then pictures can be sent from a computer to a television screen, or another example, a game can be started on a gaming console to be completed on a Smartphone. The revolution of the smart devices is in progress as well as the wireless functionality, which is unavoidable in modern devices. There is no possibility to sell a new advanced console or phone, which is no equipped with WLAN card. It changes the way to conceive the HAN since consumers use a same network to connect all these products. The general trend goes towards the use of these devices everywhere at home with high data rate connectivity between them and with a domes-tic cloud ( sometimes we call such a solution a domestic cloud) based on a storage server. As a consequence, the amount of data exchanged in the HAN should drastically increase in a near future. A sample of HAN (domestic cloud or wireless home) configuration is shown in Fig. 4.

One of the most demanding services is the exchange of uncompressed HD videos. In fact, a picture 1920x1080 matrix coded with 24 bits per pixel at 60Hz requires a data speed close to 3 Gbit/s. We can calculate the throughput, that is necessary to support HDMI using the following formulas:

(1)

where respectively:BR is the bit rate ( throughput for HDMI),M is the Matrix (the number of pixels),IP,IM are the information measure for pixel and for Matrix ( according to Shannon formula),V is the speed of data transmission (the number of pictures transmitted per 1 s).

The throughput is really about 3 Gbits/s:

The smart, interactive or just TV is another example for the need of HT or VHT. The forecast is very optimistic in this case. The continuous progress is expected in this market because practical test implementations show that there is demand for different wireless ser-



vices, The Hybrid broadband broadcast Television (HbbTV) initiative, that was available during the tennis tournament of Roland-Garros in 2011: real-time scores, match statistics, bios of all players, news, photos and a Twitter stream were broadcasted to the users through the Internet. It is expected that, in 2015, between 47% and 67% of all flat panel televisions shipped worldwide will have a network connectivity. This proportion of connected televi-sion is also growing thanks to additional devices that bring the Internet connectivity to the television different applications such as the gaming consoles (Xbox or Playstation), the op-erators’ set-top boxes, the Apple and Google TV media players.

Conclusion

WiGig uses the unlicensed 60 GHz band worldwide to provide data rates up to 7 Gbits/s. Based on the 802.11ad standard, it includes support for networking over 60 GHz (Fettweiss 2011); products with both Wi-Fi and WiGig integration will be able to transparently switch among 2.4 GHz, 5 GHz and 60 GHz networks, enabling optimal transmission channel. Wi-Fi Alliance is also developing interoperability programs based on WiGig PALs, that define wireless implementations of A/V and I/O interfaces, facilitating advanced applica-tions such as wireless docking, high-speed synchronization and connection to displays. The 802.11ad could be the first wireless standard able to compete with fixed solutions.

The evolution of wireless use cases, coupled with the extraordinary growth in the num-ber of wireless devices, has created the demand for even more wireless speed and range. Currently, there are 25 million subscribers to video streaming services such as Netflix, and untold others using free services such as YouTube for video streaming. In addition, the grow-ing number of screens inside the home from computers, Internet enabled TVs, tablets, and smart-phones – many of which run bandwidth-intensive applications such as HD video – further drives the requirements for higher performance wireless and more reliable connec-tions. The increase of wireless home devices quantity is presented in Fig. 5. The most per-spective sector is the communication with TV sets and disc players.

Are the present achievements a border for wireless technologies? During the last years it has become evident, that wireless data rates are increasing over time. The increased of data rate transmission evidently corresponds to the capacity and speed of different types of memories especially flash type memories. Higher capacity of flash memory produce new requirements concerning the data transfer rate. The memory development history shows that the maximal memory capacity doubled every 18 months and achieved the factor of 10 every 5 years.

Flash memories are the important storage technology for many ”wireless devices”, which require broadband transmission, as e.g. smart phones, game consoles, cameras, camcorders, e-book readers, and modern laptops. And as stored data needs to be transfer from one device to another, this size implicate the transmission rate requirements..

The wireless roadmap of increasing throughput is presented in Fig. 6.



Fig. 5Wireless home devices increased (history and forecast)

Source: Netgear White Paper (2012).

Fig. 6The wireless throughput roadmap




Another open question remains: will be there a need for data rates above 100 Mbit/s in future? Today already more than 50% of data transmission in mobile networks is the effect of the video streaming applications. The transmission of high definition 3D video streaming with enabled vision angle control requires about100 Mbit/s, and if users want quick down-loads of 100 times quicker than real-time of multiple streams, the 10Gbit/s to 100 Gbits/s wireless throughput will be a requirement. Could the requirements grow as far as 1 Tbits/s? This super fast transmission could reduced significantly the time of downloads so the user could utilize the application even when there will be short brakes due to e.g. loss of line of sight connection. Today it is rather difficult to predict how far the wireless technology will go.

Bibliography

Aruba White Paper (2012), 802.11ac In-Depth, Chapter 1: Technology Fundamentals, Chapter 2: RF Management Techniques, Chapter 3: Multi-User MIMO and Modulation, Aruba Networks Inc.

Cisco White Paper (2012), 802.11ac: The Fifth Generation of Wi-Fi, Technical White Paper, Cisco, August.

Dolińska I., Masiukiewicz A. (2012), Quality of service providing in WLAN networks possibilities, challenges and perspectives, Information systems in management, WULS Press, Warsaw.

Fettweis G., Guderian F., Krone S. (2011), Entering The Path Towards Terabit/s Wireless Links, EDAA.

Hiertz G.R., Denteneer D., Stibor P.L., Yunpeng Zang, Costa X.P., Walke B. (2010), The 802.11 Universe, ”IEEE Communications Magazine”, January.

Guillory J. (2012), Radio over Fiber for the future Home Area Networks, PhD Thesis, Prepared at Conservatoire National des Arts et Métiers (CNAM) ESYCOM laboratory and at France Télécom R&D - Orange Labs, RESA/ANA/ASHA Team

IEEE Std 802.11nTM-2009 Masiukiewicz A. (2013), 802.11ad - 60 GHz WLAN IMPLEMENTATION, „Elektronika”, grudzień.Netgear White Paper (2012), Next Generation Gigabit WiFi - 802.11ac, Netgear Inc.WiFi Alliance (2013), WiGig® and the future of seamless connectivity, September.

WLAN – bezprzewodowa platforma dla przyszłych usług

Streszczenie

Dotychczas opracowano wiele standardów bezprzewodowych, tym niemniej jedynie dwa z nich są powszechnie stosowane. W sektorze usług telefonii bezprzewodowej dominują telefonia komórko-wa i sieci WLAN. Liczba klientów sieci mobilnych sięga miliardów i nadal się zwiększa. Czy obecne osiągnięcia stanowią granicę dla technologii bezprzewodowych? W ostatnich latach stało się oczywi-ste, że z biegiem czasu szybkość bezprzewodowej transmisji danych zwiększy się. Otwarte pozosta-je inne pytanie: czy w przyszłości będzie zapotrzebowanie na szybkość transmisji danych powyżej



100 Mbit/s? Dziś już ponad 50% transmisji danych w sieciach mobilnych jest efektem zastosowań przesyłu strumieniowego obrazów.

Słowa kluczowe: WLAN, Wi-Fi, standard IEEE, jakość usług, 60 GHz.

Kody JEL: O33

Artykuł nadesłany do redakcji w czerwcu 2014 r.

© All rights reserved

Afiliacja:dr Iwona Dolińskadr Antoni MasiukiewiczAkademia Finansów i Biznesu Vistulaul. Stokłosy 202-787 Warszawatel.: 22 457 23 00e-mail: [email protected]: [email protected]


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WLAN – Wireless Platform for Future Services