Abstract
The IEEE 802.11ah standard relies on the conventional distributed coordination function (DCF) as a backoff selection method. The DCF is utilized in the contention-based period of the newly introduced medium access control (MAC) mechanism, namely restricted access window (RAW). Despite various advantages of RAW, DCF still utilizes the legacy binary exponential backoff (BEB) algorithm, which suffers from a crucial disadvantage of being prone to high probability of collisions with high number of contending stations. To mitigate this issue, this paper investigates the possibility of replacing the existing exponential sequence (i.e., as in BEB) with a better pseudorandom sequence of integers. In particular, a new backoff algorithm, namely Pseudorandom Sequence Contention Algorithm (PRSCA) is proposed to update the CW size and minimize the collision probability. In addition, the proposed PRSCA incorporates a different approach of CW freezing mechanism and backoff stage reset process. An analytical model is derived for the proposed PRSCA and presented through a discrete 2-D Markov chain model. Performance evaluation demonstrates the efficiency of the proposed PRSCA in reducing collision probability and improving saturation throughput, network throughput, and access delay performance.
Highlights
With the emergence of Internet-of-Things (IoT) and Machine-to-machine (M2M), the number of wireless stations has increased explosively
The major contributions of this paper are outlined as follows: We propose the use of a pseudorandom sequence to be an alternative for Binary Exponential Backoff (BEB) sequence; We propose an efficient backoff algorithm using the pseudorandom sequence to calculate the contention window size; We compute and analyse the collision probability and normalized saturation throughput of our proposed backoff algorithm with a 2-D Markov model and compare the results with BEB
The simulation details can be further elaborated as follows: 1. BEB algorithm is compared with the proposed Pseudorandom Sequence Contention Algorithm (PRSCA) in a WLAN network of 802.11ah with n = 50 contending stations, and a non-variable pre-defined payload size of 1 Kbytes (8184 bits)
Summary
With the emergence of Internet-of-Things (IoT) and Machine-to-machine (M2M), the number of wireless stations has increased explosively. Wireless network resources are to be shared by a large number of IoT-based stations, such as sensors, actuators, smartphones, and smart appliances [1] These stations are associated to various fields, such as home automation, industrial and manufacturing automation, smart grid and metering, e-health, data analysis and management, security systems, intelligent transportation systems, public surveillance, etc. The major contributions of this paper are outlined as follows: We propose the use of a pseudorandom sequence to be an alternative for BEB sequence; We propose an efficient backoff algorithm using the pseudorandom sequence to calculate the contention window size; We compute and analyse the collision probability and normalized saturation throughput of our proposed backoff algorithm with a 2-D Markov model and compare the results with BEB algorithm; We investigate the QoS performance notably throughput and delay of the proposed algorithm via MATLAB.
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