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Channel assignment strategies

Rules for channel assignment

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Channel assignment strategies

  1. 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. 2. Introduction Related Work Channel Assignment Strategy  Results Conclusions02/07/13 2
  3. 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. 4. Related WorkA Channel Assignment Strategy using Four Partially Overlapping Channels in Mid-scale Wireless Mesh Networks
  5. 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. 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. 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. 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. 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. 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. 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 (RSSIs) from all channels 11
  12. 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.
  14. 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. 15. Greedy algorithm
  16. 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 ef16 02/07/13
  17. 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 set417 02/07/13 Conflict Graph
  18. 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 818 02/07/13
  19. 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 y02/07/13 19
  20. 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. 21. Q UERRIES ?