Rules for channel assignment

1. Channel Assignment Strategies
AJAL.A.J
Assistant Professor –Dept of ECE,
Federal Institute of Science And Technology (FISAT) TM
MAIL: ec2reach@gmail.com

2. Introduction
Related Work
Channel Assignment Strategy
Results
Conclusions
02/07/13 2

3. Channel Assignment Strategies
 For efficient spectrum utilization, frequency reuse
scheme should be consistent with objectives
► Increasing system capacity
► Minimizing interference
 Strategies can be classified as
 Fixed and
 Dynamic
3

4. Related Work
A Channel Assignment Strategy using Four Partially Overlapping
Channels in Mid-scale Wireless Mesh Networks

5. Fixed Channel Assignment Strategy
 In Fixed Channel Assignment Strategy,
► Each cell is allocated a predetermined set of voice channels.
► A call attempt can only be served if unused channel in that
particular cell is available
► If all channels are occupied then the call is blocked. Several
variation exist like borrowing strategy
• A cell is allowed to borrow a channel from neighboring cell if
all of its channels are occupied
• A mobile switching center (MSC) supervises such
procedures and ensures that borrowing of channel does not
disrupt the or interfere with any of the calls in progress in
the donor cell
5

6.  Dynamic Channel Assignment Strategy
 Dynamic Channel Assignment Strategy
► Voice channels are not allocated to cells
permanently
► On each call request, the BS requests a channel
from MSC.
► MSC allocates a channel by taking into account
• the likelihood of future blocking within the cell
• The frequency of use of the candidate channel, reuse
distance
6

7. ► Hence, MSC only allocates a channel if that is not
presently in use in the cell which falls within
minimum restricted distance of frequency reuse.
► It reduces the likelihood of the call blocking,
increasing the trunking capacity of the system.
► It requires MSC to collect real-time data on channel
occupancy, traffic distribution and RSSI of all
channels
• This increases storage and computational load on the
system
• But provides increased channel utilization and decreased
call blocking
7

8. Channel Assignment Strategies
• Frequency reuse scheme
– increases capacity
– minimize interference
• Channel assignment strategy
– fixed channel assignment
– dynamic channel assignment
• Fixed channel assignment
– each cell is allocated a predetermined set of voice channel
– any new call attempt can only be served by the unused channels
– the call will be blo c ke d if all channels in that cell are occupied
• Dynamic channel assignment
– channels are not allocated to cells permanently.
– allocate channels based on request.
– reduce the likelihood of blocking, increase capacity.

9. Channel assignment strategies
 For efficient utilization of the radio spectrum, a
frequency reuse scheme is consistent with the
objectives of increasing capacity and
minimizing interference.
interference
 A variety of channel assignment strategies has
been developed: fixed or dynamic.
dynamic
 The choice impacts the performance of the
system, particularly as to how calls are
managed when a mobile is handed off from
one cell to another.

10. Dynamic channel assignment
 Dynamic channel assignment strategies require
the RNC to collect real-time data on channel
occupancy, traffic distribution, and radio
distribution
signal strength indications (RSSI) of all
channels on a continuous basis.
 This increases the storage and computational
load on the system but provides the advantage
on increased channel utilization and decreased
probability of blocked call.
 There are also hybrid strategies (Flexible
channel assignment).
assignment

11. Dynamic channel assignment
 Advantage: reduces call blocking (that is to say,
it increases the trunking capacity), and
increases voice quality
 Disadvantage: increases storage &
computational load @ MSC
 requires real-time data from entire network related
to:
 channel occupancy
 traffic distribution
 Radio Signal Strength Indications (RSSI's) from all
channels
11

12. Rules for channel assignment
 Do not assign co-channels or adjacent channels at
the same cell site (not applicable for CDMA).
 Do not assign co-channels in adjacent cell sites (not
applicable for CDMA).
 Do not mix and match channel groups in a cell or
sector.
 Avoid adjacent channel assignment in adjacent cell
sites (not applicable for CDMA).
 Maintain proper channel separation for any channel
assignment for a sector or site.
 Maximize the distance between reusing cell sites.

13. REAL TIME SCENARIO !

14. 7MHz 2MHz 7MHz
Interference
Load Balance
[1] Texas Instruments, “The Effects of Adjacent channel Rejection and Adjacent channel
interference on 802.11 WLAN Performance, ” SPLY005-Nov. 2003 White Paper
[2] Yong Ding, “Channel Assignment with Partially Overlapping Channels in Wireless Mesh
Networks, ” WICON 2008 and ICST 2008. (Michigan State University)

15. Greedy algorithm

16. FPOC Channel Assignment Strategy
a
17 b
26
19 c
d 39
29 e 19
16
28 f
38
g
23
27 h
29 i
Node order of assignment : MAPe
assigned
linkeb: 39 radio11
radio radio22
radio
assigned
linkeh: 38 linkeb: 39 linkeh: 38
assigned
link : 29 linkef: 28 linked: 29
ba
assigned
link : 28
ef
16 02/07/13

17. FPOC Channel Assignment Strategy
a LinkSet3
17 b
26
LinkSet5 39 19 c
d LinkSet1
29 e 19
16
LinkSet2 LinkSet6
28 f
38
g
23
27 h
LinkSet4
29 i
Link Link
set1 set2
Link Link
set3 set6
Link Link
set5 set4
17 02/07/13 Conflict Graph

18. FPOC Channel Assignment Strategy
a LinkSet3
17 b
26 19
LinkSet5 39 c
d LinkSet1
19
29 e
16 LinkSet2 LinkSet6
28 f
38
g
23
27 h
LinkSet4
29 i
Traffic Conflict-free Channels
LinkSet1 67 null Channel 1
LinkSet2 67 null Channel 4
LinkSet4 56 LinkSet3 Channel 8
LinkSet5 42 LinkSet6 Channel 11
LinkSet6 42 LinkSet5 Channel 11
LinkSet3 36 LinkSet4 Channel 8
18 02/07/13

19. a b c d e
f g h i j
Transmission
Range
k l m n o
Interference
Range
p q r s t
u v w x y
02/07/13 19

20. Reserved Channel Scheme (RCS)
 The reserved channel scheme (RCS) is similar to NPS
except that a number of channels or transceivers in
each BS are reserved for handoffs.
 In other words, the channels are divided into two
groups:
 the normal channels, which serve both new calls and
handoff calls,
 the reserved channels, which only serve handoff calls.

21. Q UERRIES ?