Adaptive channel assignment scheme for wireless networks

1
Adaptive channel assignment scheme for wireless
networks

• Source Computers and Electrical Engineering
  Volume 30, Issue 6, September, 2004, pp.
  417-426
• Authors Jin-Long Wang and Shu-Yin Chiang
• Speaker Kun-Ming Tsai (???)
• Date 2005/03/19

2
Outline

• Introduction
• Previous works
• Dynamic channel assignment scheme
• Simulation result
• Conclusions

3
Introduction(1/3)

• The design of effective and dynamic bandwidth
  allocation to satisfy different service demands
  is important in wireless networks.

4
Introduction(2/3)

• Another key issue in the performance
  characterization of wireless mobile networks is
  the smooth handoff.
• The simplest way of giving priority to handoff
  requests is the guard channel scheme.

5
Introduction(3/3)

• Guard Channel (GC)
• Each cell reserves a fixed number of channels
  exclusively for handoff connections.

reserve some channels for handoff ex 5GC
if no available channels, handoff channel will
drop
In this paper, Guard Channel didntdistinguish
with new and handoff data traffic.
6
SCA (single channel allocation)

• The allocation scheme attempts to uniformly
  distribute traffic in the cell among all channels
  by allocating the channel with the lowest traffic
  load measured in Kbits.

Free channel
Free channel
Free channel
Free channel
request
Free channel
Free channel
Free channel
Free channel
Free channel
7
FCA (fixed channel allocation) (1/2)

• FCA scheme For a data request of K channels, if
  the number of free channels in the system is more
  than K, the request is accepted, otherwise, it is
  rejected.

request
Request 2 channels
Request 5 channels
Free channel
Free channel
Free channel
accepted
rejected
8
FCA (fixed channel allocation) (2/2)

• Multi-channel scheme
• GPRS????(Carrier)? 8 ???(Slots)

Free channel
request
9
Dynamic channel assignment scheme (1/3)

• Markovian model

10
Dynamic channel assignment scheme (2/3)

• Hot cell
• If the number of occupied cells is greater than
  the threshold.
• Cold cell
• If the number of occupied cells is smaller or
  equal than the threshold.

11
Dynamic channel assignment scheme (3/3)

• The hot cell accepts the handoff calls, but
  accepts the new call only with the probability of
  channel assignment according to the Eq.

12
Simulation result (1/3)

• The dropping rate with different arrival rate of
  handoff call ( 1/6).

13
Simulation result (2/3)

• Blocking rate versus arrival rate of handoff call
  ( 1/6)

14
Simulation result (3/3)

• Throughput versus arrival rate of handoff call.

15
Conclusions

• Markovian model to effectively estimate the
  threshold, which indicates the number of channels
  required by handoff calls.
• If it is in hot state, the handoff call can be
  accepted with no condition, but the new call only
  can be allocated a channel with a probability.
• The proposed scheme provides QoS guarantee by
  keeping the handoff dropping rate below a desired
  level.