Browsing by Author "Wavegedara, CB"

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    item: Conference-Abstract
    A dynamic resource management scheme for two-tier LTE femtocell networks
    (2015-07-06) Wickramasinghe, CL; Wavegedara, CB
    Recently, the femtocell concept has received considerable attention both in academic and industry as a promising solution for the deep indoor coverage problem as well as the increasing data demand of mobile devices. Large scale femtocell deployments are hindered mainly by the cross tier interference problem spawned by their inherent uncoordinated deployment and the shared use of the limited spectrum resource by the macro and femtocell networks. The spectrum sharing scheme used has a high impact on the total network throughput. Balance is needed between shared and dedicated spectrum to achieve high spectral efficiency and reduce the co-channel interference. This paper proposes a new hybrid spectrum management scheme for the downlink of OFDMA based systems (e.g. LTE system). The proposed scheme dynamically changes the dedicated spectrum bands of macro and femtocell networks based on the level of interference experienced by users. The throughput performance of the proposed scheme is investigated using simulation and is shown to be considerably better than that of the widely used static spectrum partitioning.
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    Improved ldpc decoding algorithms based on min-sum algorithm
    (IEEE, 2016-04) Kumara, YVAC; Wavegedara, CB
    Low-Density Parity check (LDPC) codes offer highperformance error correction near the Shannon limit which employs large code lengths and some iterations in the decoding process. The conventional decoding algorithm of LDPC is the Log Likelihood Ratio based Belief Propagation (LLR BP) which is also known as the 'Sum-Product algorithm' which gives the best decoding performance and requires the most computational complexity and implementations with increased hardware complexity. Another simpler variant of this algorithm is used which is known as 'min-sum algorithm' which reduces computational complexity as well as hardware complexity but with reduced accuracy. This paper analyzes the reason min-sum algorithm is more prone to errors when compared to the sumproduct algorithm, and puts forward two improved algorithms which improve the performance of the min-sum algorithm with comparable algorithmic complexity.
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    item: Conference-Abstract
    A low-latency and energy efficient forward handover scheme for LTE-femtocell networks
    (2014-06-18) Dampage, U; Wavegedara, CB
    Femtocells are small, inexpensive, low power cell sites, which are used to improve indoor capacity and coverage. They are generally consumer deployed and are connected to their own wired broadband backhaul connections. A large number of femtocell deployments in long term evolution (LTE) networks are highly anticipated. One of the main technical challenges of LTE-femtocell networks is the handover between a femtocell and the macrocell due to non availability of direct communication links between femto eNBs and macro eNBs. Due to small femtocell coverage areas, frequent handovers between femtocells and macrocells take place. Therefore, a fast handover scheme using small signaling overhead is required for LTE-femtocell networks to support fast and seamless handovers. The S1-based handover scheme specified in the LTE standards for handover between eNBs, which are not directly connected through X2 interface, can also be used for handover between a femtocell and a macrocell. However, the latency of a S1-based handover increases significantly with the Internet delay as HeNBs are connected to eNBs through public Internet. In this paper, we propose a fast and efficient handover scheme to facilitate handovers between femtocells and macrocells. We also introduce a novel concept of the Temporary Area Partners (TAP) network, which consists of the mobile user equipment connected through device-to-device communication. Due to aforesaid TAP network, the proposed handover scheme will be more robust than the forward and S1-based handover schemes. Our delay performance analysis shows that the proposed scheme has much lower latency than the existing S1-based and forward handover schemes.
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    item: Conference-Full-text
    Performance investigation of hybrid arq in hsdpa systems with amc
    (IEEE, 2016-04) Liyanage, NDK; Abeywickrama, CA; Kumari, PMIU; De Silva, SA; Wavegedara, CB; Jayasekara, AGBP; Bandara, HMND; Amarasinghe, YWR
    In the world of telecommunication, demand for 3G mobile communication services still dominates the global market. It continues to grow despite the introduction of new technologies such as LTE and LTE-A. Hybrid Automatic Repeat Request (HARQ) and Adaptive modulation and coding (AMC) are among the key performance enhancing techniques adopted in High Speed downlink packet access (HSDPA). Limiting the maximum number of HARQ retransmissions in downlink is important to save the radio resources. In this paper, we investigate the throughput and error performance of HSDPA systems employing HARQ and AMC, for different mobile receiver speeds. Furthermore, the impact of turbo equalization on the performance is also investigated. A method to obtain the optimal value for the maximum number of HARQ retransmissions in HSDPA is proposed.