Journal of Wireless Networking and Communications 2016, 6(3): 66-72 DOI: 10.5923/j.jwnc.20160603.02 Partial Contention Free Random access Protocol for M2M communications in LTE Networks Ahmed Samir 1 , Mahmoud M. Elmesalawy 2 , Ahmed Salah EL-Din Ali 2,* , Ihab Ali 2 1 IT Dept., Etisalat-Egypt, Cairo, Egypt 2 Electronics, Communications and Computers Department, Helwan University, Cairo, Egypt Abstract The current specifications of the Random Access Channel (RACH) of the Long Term Evolution (LTE) and LTE-Advanced (LTE-A) is not appropriate for Machine-to-Machine (M2M) communications. This is because the massive number of M2M devices will lead to low access rate and large access delay. This paper presents a new protocol, based on the Distributed Queuing (DQ) algorithm, for improving the performance of the Random Access (RA) procedure of LTE to support the M2M services. The proposed protocol, Distributed Queuing Access for LTE (DQAL), minimizes the opportunity of collision in the access phase for M2M. The reduction in the collision will turn in enhancing both the access rate and the access delay. Furthermore the presented scheme is designed to keep the normal access procedures of Human-to-Human (H2H) communication without any impact. Results show that the access delay is decreased to half of the LTE access delay and the access success probability approaches unity. Keywords Distributed Queuing, LTE, Machine-to-Machine, Random Access Channel 1. Introduction The M2M communication introduced a huge number of low rate connections with long sleeping period in order to save the power [1]. The current implementation of the RACH in the LTE and LTE-A is not suitable for this type of communication. This is one of the major reasons that made the 3GPP emphasize the need to revise the design of RACH in the next-generation cellular networks. Accordingly, there are many research works are proposed to improve the performance of the RACH procedure in LTE to support M2M communications [2-6]. Optimized MAC which is based on transmitting the data of M2M devices either in RACH message 1 (preamble) or in message 3 (terminal identification message) [2]. This will be suitable for M2M applications having very small amount of data. Access Class Barring (ACB) which is based on defining 16 different classes with different priorities and back-off time for various traffic types [3]. Indeed, it is specified as a mechanism to control the access to the air interface in LTE and LTE-A [4]. On the other hand, some studies coincide in suggesting that the ACB should not be used as a stand-alone solution to solve the congestion problem in the MTC networks [5] [6]. In dynamic allocation of RACH resources, the network allocates more Random * Corresponding author: ahmed.elkomy87@gmail.com (Ahmed Salah EL-Din Ali) Published online at http://journal.sapub.org/jwnc Copyright © 2016 Scientific & Academic Publishing. All Rights Reserved Access (RA) slots for M2M devices if the radio access is under congestion [7]. Slotted access schema is based on assigning dedicated access resources for each single M2M terminal is proposed in [8]. Prioritized Random Access (PRA) is based on assigning different number of virtual resources for different traffic classes [3]. In case of overload, there are certain classes will be barred to minimize the collision probability. Self-Optimized Overload Control (SOOC) is continuously configure the RA resources based on the load condition [2]. Code-expanded RA which increases the access opportunities by using the code expanded RA instead of using more preambles or RA slots [9]. All of the above proposals are based on ALOHA and slotted ALOHA multiple access techniques even though they have low throughput and possible instability under heavy load. There is another approach for improving the RACH which is based on the tree algorithm and the Distributed Queuing Random Access Protocol (DQRAP). The main concept of DQRAP depends on using a number of control minislots as access opportunities. The protocol operates as random access protocol in the light traffic case and switches automatically to a reservation protocol when traffic becomes heavy [10]. DQRAP was suggested by [11] to enhance the random access channel in Code Division Multiple Access (CDMA). It is also used to improve the throughput of the WLAN as proposed in [12]. All of these studies proved the stability of the protocol and its near-optimum behavior in terms of access delay, channel utilization and power consumption.