Study of Latency in Enhanced-PGLU (EPGLU) Timer Based Paging in IEEE 802.16m based WiMAX Networks Vivek Kumar Singh, Ritesh Kumar Kalle and Debabrata Das International Institute of Information Technology-Bangalore, Electronic City, Bangalore-560100, India Email: vivekkumar.singh@iiitb.net, {riteshkumar.k, ddas}@iiitb.ac.in Abstract—Paging latency is one of the important parameters for determining the Quality of Service (QoS) required by the telecom and broadband applications. Most of the 4G applications (especially real time applications) require upper bound on paging latency. In this paper, authors have provided a novel algorithm for Enhanced-PGLU (EPGLU) to reduce the paging delay and have provided the comparative study of paging latency in EPGLU timer based paging with respect to the PGLU (Paging Group Location Update) timer based paging available in forth coming IEEE 802.16m standards. The results show 27% decrease in paging latency with EPGLU based proposed algorithm as compared to PGLU based paging provided in IEEE 802.16m standards. Key words: IEEE 802.16m, idle mode, Paging, Paging overhead, Location Update, paging latency, EPGLU, PGLU I. I NTRODUCTION 4G broadband wireless technology is the need of future applications due to better Quality of Service (QoS) and Quality of Experience (QoE) requirement. Paging and Location Update are two important procedures of any future telecom technolo- gies. Paging is the procedure by which the Paging Controller (PC) locates the Mobile Station (MS) when there is downlink data available for the MS. Location Update is the procedure in which the MS updates its location to the PC at regular interval of time and also with the change in Paging Group [1]. The forth coming telecom applications require guaranteed QoS in terms of bandwidth and latency (like real time applications). To achieve a critical upper bound on the latency, paging and location update of the MS should consume less time. Paging latency [1] and paging overhead [16] are two critical aspect of the Paging Group Location update in Mobile WiMAX IEEE 802.16m standards [8]. A. PGLU Timer based paging According to IEEE 802.16m standard, the paging groups in the WiMAX network are divided into two segments with respect to location of MS. One is called Primary Paging Group (PPG) and another is called Secondary Paging Group. The details of PPG and corresponding SPG (s) are maintained in the Location register (LR) maintained by Paging Controller known as Anchor Paging Controller (APC). When a MS moves out of PPG into SPG in idle mode, it starts PGLU (Paging Group Location Update) timer. The value of PGLU timer is generally less than the idle mode timeout value. If the MS returns back to the PPG within the expiry of PGLU timer, no location update is performed. If the MS does not return back to PPG with the expiry limit of PGLU timer, location update is performed by MS. This approach reduces the effective number of location update performed by the MS but does not take into account the relative distance of MS from PPG. As the location update is not performed before the expiry of PGLU timer, even if the MS is relatively far from PPG. This leads to increase in paging area and in turn increase in paging latency. The solution to this problem is provided by authors in next section as Enhanced PGLU (EPGLU) timer based paging. B. EPGLU Timer based paging Authors have presented Enhanced PGLU (EPGLU) timer based paging mechanism in this sub-section. According to above mentioned algorithm, the SPG is further subdivided into small PG called Sub-Secondary paging group (sub-SPG) depending on the relative distance from the PPG. Each of the Sub-SPG is assigned with EPGLU timer and its value decreases with increase in the distance from the PPG. When a MS moves out from PPG in idle mode, the EPGLU timer for the particular Sub-SPG is initialized for the MS. If the MS returns back to PPG within the expiry of the EPGLU timer for the particular Sub-SPG, it does not perform location update. If the MS does not return back to PPG within the expiry of the EPGLU timer for the Sub-SPG where the MS is currently located, it performs the location update. But, unlike the PGLU timer based approach, if the MS moves within the SPG and moves relatively away from PPG, then the EPGLU timer value of the MS decreases with increase in relative distance from PPG. This is because, the MS which moves relatively away from the PPG has less chance to return back to PPG, hence, should perform location update to reduce paging latency to locate the MS. As discussed above, upper bound on paging latency is one of the essential parameters for guranteed QoS and QoE required for the future application. In this paper, authors have presented a novel algorithm for paging the MS as EPGLU Timer based paging for 802.16m. In addition to this, authors have also presented the comparative study of paging latency 978-1-4577-1328-6/11/$26.00 2011 IEEE 1