scholarly journals Design and Modeling of Self-Adapting MAC (SaMAC) Protocol with Inconstant Contention Loss Probabilities

2018 ◽  
Vol 2018 ◽  
pp. 1-25
Author(s):  
Ante Kristić ◽  
Julije Ožegović ◽  
Ivan Kedžo
Keyword(s):  
Wireless Networks ◽  
Mac Protocol ◽  
Markov Chain Model ◽  
Loss Probability ◽  
Chain Model ◽  
Industrial Wireless Networks ◽  
802.11 Dcf ◽  
Loss Probabilities ◽  
Congested Networks ◽  
A Chain

Networks based on IEEE 802.11 standard are one of the main options for deployment in industrial environment. Degradation of throughput in congested networks and short-term unfairness are well-known drawbacks of 802.11 DCF and similar MAC protocols. Those shortcomings represent significant limitation in forecasted growth of wireless usage. This is especially important in industrial wireless networks (IWN) where the scalability of wireless MAC is one of the main requirements. In this paper, a novel self-adapting MAC protocol (SaMAC) is defined and mathematically modeled. SaMAC employs constrained countdown freezing enhanced with shifted window mechanism. As a result, the protocol outperforms 802.11 DCF standard as well as shifted contention window (SCW) and constrained countdown freezing (CPCF) protocols in achieved throughput, fairness, and jitter, while keeping simple implementation. Despite protocol’s simple design, it is shown that its mathematical model is extremely complex. For proposed protocol, the assumption of constant contention loss probability, which is normally used for modeling of MAC schemes, does not hold. In the presented multidimensional Markov chain model, a unique iterative method for determining contention loss probability is developed as well as a method for throughput calculation based on such a chain. Accuracy of the presented model is verified in several network scenarios. Considering the performance of the proposed protocol, authors believe that it could be of benefit to deploy it in heavily loaded wireless networks with timing constraints, such as IWNs.

PERFORMANCE EVALUATION OF A REQUEST-TDMA/CDMA PROTOCOL FOR WIRELESS NETWORKS

2001 ◽  
Vol 02 (01) ◽  
pp. 49-67 ◽  
Author(s):  
MAINAK CHATTERJEE ◽  
SAJAL K. DAS
Keyword(s):  
Wireless Networks ◽  
Waiting Time ◽  
Multiple Access ◽  
Transition Probabilities ◽  
Mac Protocol ◽  
Markov Chain Model ◽  
Time Frame ◽  
Chain Model ◽  
Request Message ◽  
Code Division Multiple

This paper proposes a new medium access control (MAC) protocol, called Request-TDMA/CDMA, for supporting multimedia traffic in wireless networks. In this hybrid protocol, CDMA (code division multiple access) is laid over TDMA (time division multiple access), where a time frame has two kinds of slots, namely data slots and control slots. The data slots are used to the user to transmit their data while the control slot holds the information for the next frame's slot allocation. Each data slot in a frame can be simultaneously used by multiple users with the help of uniquely assigned codes. Whenever a user needs to transmit a message, he first sends a request message to the central controller and enters the contention process. The controller takes into consideration the time of generation of a call, the bit rate requirement and the message length while reserving slots for the entire length of the message generated. The user then goes into the transmission phase if he is successful in the contention process, and continues to transmit his data till the entire message is sent. Three scheduling algorithms for the allocation of data slots are proposed and their performance are studied for four classes of traffic. We also analyze our protocol using a two-dimensional Markov chain model, and compute the state transition probabilities and derive the average waiting time for a given system load. By simulation experiments we show that our request-TDMA/CDMA protocol is able to effectively combine the orthogonality of both time and code division multiplexing. Further enhancements are also proposed to decrease the waiting time and increase the average channel utilization.

Analysis of the Multi-Channel MAC Protocols in Wireless Networks

2013 ◽  
Vol 756-759 ◽  
pp. 2734-2738
Author(s):  
Chun Guang Shi ◽  
Hai Tao Zhao ◽  
Yi Tang ◽  
Yun Feng Zhou
Keyword(s):  
Wireless Networks ◽  
Markov Chain ◽  
Single Channel ◽  
Mac Protocol ◽  
Markov Chain Model ◽  
Mac Protocols ◽  
Protocol Design ◽  
Network Throughput ◽  
Chain Model

This paper discusses the problems that may be encountered in a multi-channel MAC protocol design. Furthermore, the normalization network throughput of multi-channel MAC is analyzed based on a Markov chain model. The simulation shows that compared to single channel 802.11, multi-channel MAC can improve the normalization network throughput. Moreover, the greater is the number of divided sub-channels, the higher is the normalization network throughput.

A Backoff Algorithm for LOWPAN Based on the Dynamically Backoff Exponent

2015 ◽  
Vol 713-715 ◽  
pp. 1389-1393
Author(s):  
Ya Jun Zhang ◽  
Jin Liang Shi ◽  
Guo Rong Chen
Keyword(s):  
Ieee 802.15.4 ◽  
Mac Protocol ◽  
Markov Chain Model ◽  
Poor Performance ◽  
System Throughput ◽  
Chain Model ◽  
Backoff Algorithm ◽  
The Poor ◽  
Mathematical Derivation ◽  
Transmission Status

A mechanism that the backoff exponent changes dynamically was proposed aiming at the poor performance of backoff algorithm in IEEE 802.15.4 MAC protocol. The algorithm could adjust the initial backoff exponent according to the previous transmission status and the backoff exponent. A Markov chain model for the algorithm was established and the mathematical derivation for the model was carried out. The theoretical analysis and simulation results show that the model increases the channel access probability and system throughput. The optimized algorithm improves the performance of LOWPAN effectively.

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