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Centralized vs. distributed paging architecture In centralized paging architecture, there is no issue – DID works perfectly. In distributed paging architecture, more than one PCs may involve in the DID assignment within a PG – Collisions occur. –Collisions also occur while using MAC address. –DID may have higher collision probability. PG-x A-ASN GW-1A-ASN GW-2A-ASN GW-3 Serv GW AA for AMS1AA for AMS2 APC for AMS1APC for AMS2 AMS-1AMS-2 ＊ Distributed paging architecture

Analysis model – DID collision N: the number of PCs associated with PG A. –PC n has x n AMSs under control in PG A. B: total number of IDs in the ID pool. –E.g. B = 2 24 for MAC address hash, B = 2 21 for DID(12)+paging_offset(9) Assumptions –1: Each PC records which IDs it has already assigned to AMSs. –2. Each PC randomly assigns ID to AMSs from the set of IDs that are not in use. –3. Each PC assigns an ID at a time. –4. Idle mode entry to PC 1 to PC N are uniformly distributed. Conditional probability –Knowing that there are x n AMSs in PG A controlled by PC n, n=1, 2, …, N, and no ID collision occurs. –Now an AMS is joining PG A, and its corresponding paging controller, PC i wants to assign an ID to the AMS in the PG, then Pr{No collision of newly assigned ID | No ID collision among (  N n=1 x n ) ID assignments in the PG} = (B –  N n=1 x n ) / (B – x i ).

Collision probability results 1- P r (collision prob.) Number of AMSs in PG A (N=5) MAC address hash (24 bits) 9.537* * * * *10 -4 DID (12 bits) + P. offset (12 bits) 9.537* * * * *10 -4 DID (12 bits) + P. offset (9 bits) (P. cycle = 512) 7.631* * * * *10 -3 DID (12 bits) + P. offset (8 bits) (P. cycle = 256) 1.526* * * * *10 -3 DID (12 bits) + P. offset (7 bits) (P. cycle = 128) 3.054* * * * *10 -2 DID (12 bits) + P. offset (6 bits) (P. cycle = 64) 6.112* * * * *10 -2

Damages caused by false-alert paging (DID design) Assume that the “Idle Mode Retain Information element” parameter is configured by 0b1110 during the idle mode negotiation. –AAI_SBC-REQ/RSP can be omitted (network reentry) –AAI_PKM-REQ/RSP can be omitted (network reentry) –AAI_REG-REQ/RSP can be omitted (network reentry) Damages are mainly caused by unnecessary AAI_RNG-REQ/RSP message exchanges for network re-entry –AAI_RNG-REQ requires 220 bits (including AGMH) –AAI_RNG-RSP requires 82 bits (including AGMH)

Paging overhead saving by applying current DID design In AAI_PAG-ADV –DID(12)+ p.cycle(4) = 16 bits –MAC address hash = 24 bits –24-16 = 8 bits saving In AAI_RNG-REQ (Network re-entry) –DID(12)+p.cycle(4)+p.offset(12)+PGID(16) = 44 bits –MAC address = 48 bits –48-4 = 4 bits saving Totally we can save 12 bits for each paged AMS.

Pure overhead saving by applying current DID design

Different profiles The network may provide various services, each has different call latency requirement. –e.g., the user subscribing VoIP service may be assigned a small paging cycle, since VoIP service may require small call latency. –e.g., the user subscribing best-effort service may be assigned a large paging cycle. Three profiles are considered in our analysis. Paging Cycle (in superframes) Profile #160%10% Profile #210% 60% Profile #320% ＊ Total number of users in one PG = 10,000

Analysis results

Conclusions DID can save significant paging overheads for either the centralized or distributed paging architecture. In the distributed paging architecture, we may apply several collision-avoidance solutions for having more overhead saving. For the network that is not ready to apply the DID system, “Network Configuration” in S-SFH SP2 can be set to 1 to keep using the MAC address hash.