Hop reservation multiple access
(HRMA) for multichannel
packet radio networks
Zhenyu Tang; Garcia-Luna-Aceves, J.J.
Computer Communications and
Networks, 1998. Proceedings. 7th
International Conference on , 1998
Outline
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Introduction
HRMA Protocol
Comparative Throughput Analysis
Numerical Results
Conclusions
Introduction(1)
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radios operate using two spread spectrum
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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
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ALOHA
slotted ALOHA
sender- or receiver-oriented code assignments
Introduction(2)
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proposed paper
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based on very slow frequency hopping
allows to reserve a frequency hop (channel)
provides a baseline to offer QoS in ad hoc
networks
based on simple half-duplex slow FHSS radios
HRMA Protocol(1)
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based on common hopping sequence
no carrier sensing
L available channel
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Denote by f0 the synchronization channel
exchange synchronization information
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synchronization period
beginning of a frequency hop and the current hop
the rest channels
HRMA Protocol(2)
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the rest channels
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frequency pairs (fi,fi*),i=1,2…….M
frequency hop fi
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frequency hop fi*
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HR packet, RTS, CTS, data packet
ACK packet
HRMA slot
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synchronization period
HR period (Hop Reservation)
RTS period
CTS period
HRMA Protocol(3)
HRMA Protocol(4)
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new node
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to join with HRMA
create one-node system
HRMA Protocol(5)
backoff
during CTS preiod
t7
S_RTS
WF_CTS
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t2
t11
t9
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t12
t5
t4
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t2
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WF_HR
t4
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t10
t8
more data
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WF_DATA
t13
t1
t3 t6
S_HR
idle
end of transmission
S_DATA
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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 HR, send RTS in
RTS period
t5:the reserved slot starts and HR, send RTS
immediately
t6:data received or timeout and LD
t7:timeout and HR, 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: t 7 and receive RTS, send CTS in CTS
period
t12:after CTS period of the reserved slot
t13:end of HR packet transmission
no synchr. infor. , send synchr.
packet
join
start
synchr. infor.
HRMA Protocol(6)
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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 HR , send RTS in RTS period
t5:the reserved slot starts and HR, send RTS immediately
t6:data received or timeout and LD
t7:timeout and HR, 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: t 7 and receive RTS, send CTS in CTS period
t12:after CTS period of the reserved slot
t13:end of HR packet transmission
Comparative Throughput Analysis(1)
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assumption
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N nodes, M frequency hops
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a fully-connected network
Radios are half-duplex
M>N
a typical multi-hop packet radio network
compared protocol
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ideal protocol with ROCA
ALOHA with ROCA
Comparative Throughput Analysis(2)
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ROCA (receiver-oriented channel assignment)
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unique channel to receive
tunes its radio to the channel of the intended
receiver to transmit a packet
two possible types of conflict
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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)
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ideal protocol with ROCA
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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)
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ALOHA with ROCA
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consider here a slotted ALOHA
assumption
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transmitting has the highest priority
transmitting preempts any receiving
Numerical Results(1)
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network parameters
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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
2
4
10
Numerical Results(7)
Throughput comparison: HRMA, Ideal and ALOHA
Conclusion
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offer QoS in ad hoc networks
reserve a frequency hop
better with large data packet
continues to develop multi-hop packet-radio
networks