Hop reservation multiple access (HRMA) for multichannel packet radio netw

orksZhenyu Tang; Garcia-Luna-Aceves, J.J.Computer Communications and Networks, 1998. Proceedings. 7th International

Conference on , 1998

Outline

Introduction HRMA Protocol Comparative Throughput Analysis Numerical Results Conclusions

Introduction(1)

radios operate using two spread spectrum direct-sequence spread spectrum (DSSS) frequency-hopping spread spectrum (FHSS)

focuses on an efficient MAC protocol based on FHSS radios operating

prior examples of MAC protocols ALOHA slotted ALOHA sender- or receiver-oriented code assignments

Introduction(2)

proposed paper based on very slow frequency hopping allows to reserve a frequency hop (channel) provides a baseline to offer QoS in ad hoc networ

ks based on simple half-duplex slow FHSS radios

HRMA Protocol(1)

based on common hopping sequence no carrier sensing L available channel

Denote by f0 the synchronization channel exchange synchronization information

synchronization period beginning of a frequency hop and the current hop

the rest channels

HRMA Protocol(2)

the rest channels frequency pairs (fi,fi*),i=1,2…….M frequency hop fi

HR packet, RTS, CTS, data packet frequency hop fi*

ACK packet

HRMA slot synchronization period HR period (Hop Reservation) RTS period CTS period

HRMA Protocol(3)

HRMA Protocol(4)

new node to join with HRMA create one-node system

HRMA Protocol(5)

backoff S_RTS

idle

WF_CTS

S_DATAWF_DATA

WF_HR

t9

t7

t1

t6

t8

t3

t4t2t5

t10

t11

during CTS preiod

more data

t12

end of transmission

2t

S_HR

t13

4t

t1:receive RTS, send CTS in CTS period t2:receive CTS, send data t3:more data, send HR in the next HR period t4:LD before RTS period and , send RTS in

RTS period t5:the reserved slot starts and HR, send RTS

immediately t6:data received or timeout and t7:timeout and , send RTS in RTS period t8:more data , send HR in the reserved slot of

next HR frame t9: timeout and LD t10:end of transmission and no more data t11: and receive RTS, send CTS in CTS

period t12:after CTS period of the reserved slot t13:end of HR packet transmission

startjoinsynchr. infor.

no synchr. infor. , send synchr. packet

HR

HRLD

7t

HRMA Protocol(6)

t1:receive RTS, send CTS in CTS period t2:receive CTS, send data t3:more data, send HR in the next HR period t4:LD before RTS period and , send RTS in RTS period t5:the reserved slot starts and HR, send RTS immediately t6:data received or timeout and t7:timeout and , send RTS in RTS period t8:more data , send HR in the reserved slot of next HR frame t9: timeout and LD t10:end of transmission and no more data t11: and receive RTS, send CTS in CTS period t12:after CTS period of the reserved slot t13:end of HR packet transmission

HR

LDHR

7t

Comparative Throughput Analysis(1) assumption

a fully-connected network Radios are half-duplex

N nodes, M frequency hops M>N a typical multi-hop packet radio network

compared protocol ideal protocol with ROCA ALOHA with ROCA

Comparative Throughput Analysis(2) ROCA (receiver-oriented channel

assignment) unique channel to receive tunes its radio to the channel of the intended

receiver to transmit a packet two possible types of conflict

two or more nodes try to start sending packets to the same receiver at the same slot.

the destination is transmitting or receiving

Comparative Throughput Analysis(3) ideal protocol with ROCA

there is no the two conflicts of ROCA when the first conflict happens, the ideal protocol

can randomly pick one competing sender block all the attempting senders when the second

case happens The only issue that affects the throughput is the

pair-up of nodes

Comparative Throughput Analysis(4) ALOHA with ROCA

consider here a slotted ALOHA assumption

transmitting has the highest priority transmitting preempts any receiving

Numerical Results(1)

network parameters M : frequency hops available N : the number of nodes APL : value of average packet length

depict the throughput per node (S) as a function of offered load (G)

Numerical Results(2)

Throughput of HRMA with different values of APL

Numerical Results(3)

Throughput of HRMA with different numbers of nodes

Numerical Results(4)

Throughput of HRMA with different numbers of channels

Numerical Results(5)

Throughput of Ideal protocol with different population and APL’s

Numerical Results(6)

Throughput of ALOHA with different population and APL’s

10

4

2

Numerical Results(7)

Throughput comparison: HRMA, Ideal and ALOHA

Conclusion

offer QoS in ad hoc networks reserve a frequency hop better with large data packet continues to develop multi-hop packet-radio n

etworks