Mangalam Ramakrishnan Shajan

Institute for Infocomm Research, Tumasik, Singapore

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Publications (10)0 Total impact

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    David Tung Chong Wong, Francois P. S. Chin, Mangalam Ramakrishnan Shajan, Yong Huat Chew
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    ABSTRACT: An analytical formulation of the saturated throughput of burst mode prioritized contention access (PCA) with hard distributed reservation protocols (DRPs) and beacon period (BP) in WiMedia MAC is presented. The analytical framework is formulated for one hard DRP class and N PCA classes. The state transition diagram for the ith priority PCA class is modeled by a tri-dimensional discrete-time Markov chain. One dimension of the Markov chain is for the backoff stage, the second dimension is for the value of the backoff counter, while the third dimension is mainly for the delay due to DRP transmissions or BP. The probability of the number of consecutive DRP MASs and the number of consecutive PCA MASs are derived, taking into consideration of all possible combinations of the DRP locations in a superframe. These probabilities are essential for the modeling of the Markov chain.
    WCNC 2008, IEEE Wireless Communications & Networking Conference, March 31 2008 - April 3 2008, Las Vegas, Nevada, USA, Conference Proceedings; 01/2008
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    ABSTRACT: An analytical formulation of the saturated throughput of prioritized contention access (PCA) in the presence of hard and soft distributed reservation protocols (DRPs) and beacon period (BP) in WiMedia MAC is presented. The analytical framework is formulated for one Hard DRP class, one Soft DRP class and N PCA classes. The state transition diagram for the ith priority PCA class is modeled by a tri-dimensional discrete-time Markov chain. One dimension of the Markov chain is for the backoff stage, the second dimension is for the value of the backoff counter, while the third dimension is mainly for the delay due to DRP transmissions or BP. Numerical results of the saturated throughput corresponding to typical parameter values as well as for higher data rates are presented. A method to achieve higher saturated throughput in WiMedia MAC is also illustrated in the numerical results section.
    Ultra-Wideband, 2007. ICUWB 2007. IEEE International Conference on; 10/2007
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    ABSTRACT: An analytical formulation of the saturated throughput enhancement of IEEE 802.11e using double increment plus one/ minus one half decrement (DIPO/MOHD) backoff mechanism for multiclass traffic is presented The analytical framework is formulated for N classes. The state transition diagram for the ith priority class is modeled by a two-dimensional discrete-time Markov chain One dimension of the Markov chain is for the backoff stage, and the second dimension is for the value of the backoff counter. The backoff stage moves to its previous backoff stage after a successful packet transmission and not back to the backoff stage 0 as in IEEE 802. lie. The advantages of this backoff mechanism are that it is easy to be implemented and can enhance the saturated throughputs. Numerical results of the saturated throughput corresponding to typical parameter values are presented The results show that the total saturated throughput using DIPO/MOHD can be better than that of IEEE 802. lie by up to 19%.
    Personal, Indoor and Mobile Radio Communications, 2007. PIMRC 2007. IEEE 18th International Symposium on; 10/2007
  • Source
    David Tung Chong Wong, Francois P. S. Chin, Mangalam Ramakrishnan Shajan, Yong Huat Chew
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    ABSTRACT: An analytical formulation of the saturated throughput of prioritized contention access (PCA) in the presence of hard distributed reservation protocols (DRPs) and beacon period (BP) in WiMedia MAC (formerly multi-band OFDM alliance (MBOA) MAC) is presented. The analytical framework is formulated for one hard DRP class and N PCA classes. The state transition diagram for the ith priority PCA class is modeled by a tri-dimensional discrete-time Markov chain. One dimension of the Markov chain is for the backoff stage, the second dimension is for the value of the backoff counter, while the third dimension is mainly for the delay due to DRP transmissions or BP. Numerical results of the saturated throughput corresponding to typical parameter values are presented.
    IEEE Wireless Communications and Networking Conference, WCNC 2007, Hong Kong, China, 11-15 March, 2007; 01/2007
  • Source
    David Tung Chong Wong, Francois P. S. Chin, Mangalam Ramakrishnan Shajan, Yong Huat Chew
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    ABSTRACT: An analytical formulation of the saturated throughput of prioritized contention access (PCA) in the presence of soft distributed reservation protocols (DRPs) and beacon period (BP) in WiMedia MAC (formerly multi-band OFDM alliance (MBOA) MAC) is presented. The analytical framework is formulated for one soft DRP class and N PCA classes. The state transition diagram for the ith priority PCA class is modeled by a tri-dimensional discrete-time Markov chain. One dimension of the Markov chain is for the backoff stage, the second dimension is for the value of the backoff counter, while the third dimension is mainly for the delay due to DRP transmissions or BP. Numerical results of the saturated throughput corresponding to typical parameter values are presented.
    Proceedings of the 65th IEEE Vehicular Technology Conference, VTC Spring 2007, 22-25 April 2007, Dublin, Ireland; 01/2007
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    ABSTRACT: An analytical formulation of the saturated delay of prioritized contention access (PCA) in the presence of hard distributed reservation protocols (DRPs) and beacon period (BP) in WiMedia MAC is presented The analytical framework is formulated for one Hard DRP class and N PCA classes. The state transition diagram for the ith priority PCA class is modeled by a tridimensional discrete-time Markov chain. One dimension of the Markov chain is for the backoff stage, the second dimension is for the value of the backoff counter, while the third dimension is mainly for the delay due to DRP transmissions or BP. A numerical resuU of the saturated delay corresponding to typical parameter values is presented.
    01/2007;
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    ABSTRACT: An analytical formulation of the saturated throughput of a Cooperative MAC in IEEE 802.11n for multiclass traffic is presented. A helper node is used to relay packets from the source node or access point (AP) to the destination node within a circular coverage. The analytical framework is formulated for N classes, K data rates and their corresponding K distances. The saturated throughput analysis for multiclass traffic is formulated using a two- dimensional discrete-time Markov chain rather than using an approximation. The critical probability that a helper node exists in a region to relay a packet is explicitly derived. Closed-form result for the saturated delay is also derived. Numerical results of the saturated throughput corresponding to typical parameter values are presented. The results show that the total saturated throughput using Cooperative MAC can be better than that of IEEE 802.11n using direct transmissions by up to 67% and the saturated delays using Cooperative MAC are also better than those of IEEE 802.11n.
    Proceedings of the 66th IEEE Vehicular Technology Conference, VTC Fall 2007, 30 September - 3 October 2007, Baltimore, MD, USA; 01/2007
  • David Tung Chong Wong, Francois P. S. Chin, Mangalam Ramakrishnan Shajan, Yong Huat Chew
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    ABSTRACT: An analytical formulation of the saturated throughput of Prioritized Contention Access (PCA) with Hard Distributed Reservation Protocols (DRPs) and Beacon Period (BP) in the presence of bit error for WiMedia MAC is presented. The analytical framework is formulated for one Hard DRP class and N PCA classes. The state transition diagram for the ith priority PCA class is modeled by a tri-dimensional discrete-time Markov chain. One dimension of the Markov chain is for the backoff stage, the second dimension is for the value of the backoff counter, while the third dimension is mainly for the delay due to DRP transmissions or BP. Numerical results of the saturated throughput corresponding to data rate of 1 Gbps are presented.
    Proceedings of the Global Communications Conference, 2007. GLOBECOM '07, Washington, DC, USA, 26-30 November 2007; 01/2007
  • Peng-Yong Kong, M.R. Shajan
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    ABSTRACT: In the past few years, ultra-wideband (UWB) has emerged as a radio transmission scheme for short-range wireless communications. Its various benefits have attracted interests in studying UWB technologies in both academia and industry. Currently, several MAC protocols are being proposed for UWB networks. A number of these protocols are direct adaptations from the existing MAC protocols that have been designed for narrowband systems, and thus do not make use of the UWB's unique characteristics. In contrary, there are UWB MAC protocols that incorporate dynamic channel coding after revealing that it is unique for UWB channels to exhibit a linear Shannon capacity function with respect to signal-to-noise ratio (SNR) at the receiver. We show in this paper another characteristic of a UWB channel. Specifically, for a given bit error rate and a transmission rate, the optimal ratio of interfering distance to transmitting distance may become less than unity in a UWB channel as compared to a value larger than unity in a narrowband system. This implies UWB can effectively support concurrent transmissions within the receiving range of a receiver node as long as they are outside an exclusion region given by the optimal distance ratio. In view of this, this paper further propose a CSMA/CA based MAC protocol called medium access control with concurrent transmissions (CT-MAC) to capitalize on this UWB characteristic. Simulation results indicate that CT-MAC improve the throughput-delay performance by allowing concurrent transmissions without compromising the bit error rate requirement.
    Vehicular Technology Conference, 2005. VTC 2005-Spring. 2005 IEEE 61st; 01/2005
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    ABSTRACT: Embedded wireless communication devices nowadays are getting more and more sophisticated and running at higher speeds than ever before. In order to achieve the flexibility of design and shorten the time-to-market, a firmware/hardware co-design approach is being adopted more often. The IEEE 802.11a MAC layer design conducted at the Institute for Infocomm Research uses this concept to realize the full potential of the protocol and at the same time provide the flexibility for future upgrade. This paper explains in detail the process of firmware/hardware co-design and the rationale behind our approach.
    Information, Communications and Signal Processing, 2003 and the Fourth Pacific Rim Conference on Multimedia. Proceedings of the 2003 Joint Conference of the Fourth International Conference on; 01/2004