The Experts below are selected from a list of 75 Experts worldwide ranked by ideXlab platform
K J R Liu - One of the best experts on this subject based on the ideXlab platform.
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differential space frequency modulation via smooth Logical Channel for broadband wireless communications
IEEE Transactions on Communications, 2005Co-Authors: K J R LiuAbstract:In this letter, a differential space-frequency modulation (DSFM) scheme is proposed for multiple input multiple-output (MIMO)-orthogonal frequency-division multiplexing (OFDM) systems in broadband wireless communications. We assume that the fading Channels keep constant only within each OFDM block, and may change independently from one OFDM block to another. The differential schemes proposed for MIMO-OFDM systems in the literature cannot successfully decode with such a rapidly fading Channel, since the successful decoding of the previously existing schemes relies on the assumption that the fading Channel keeps constant within a period of several OFDM blocks, and it changes slowly from a period of several OFDM blocks to another. In our proposed DSFM scheme, the transmitted signals are differentially encoded in the frequency domain within each OFDM block. Thus, the differential decoding can be performed over subcarriers within each single OFDM block. Furthermore, if a statistical Channel power-delay profile (PDP) is known at the transmitter, we propose to create a smooth Logical Channel to improve the performance of the DSFM scheme. We obtain the smooth Logical Channel by sorting the Channel frequency responses over subcarriers from a statistical point of view. If the Logical Channel is not smooth enough, we further consider a pruning process in which we use only the "good" part of the Channel and get rid of the "bad" part of the Channel. Simulation results show that the proposed DSFM scheme over a smooth Logical Channel (with pruning, if necessary) performs well for various Channel PDPs.
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differential space frequency modulation for mimo ofdm systems via a smooth Logical Channel
Global Communications Conference, 2004Co-Authors: K J R LiuAbstract:In this paper, a differential space-frequency modulation (DSFM) scheme is proposed for MIMO-OFDM systems with assumptions that the Channel keeps constant only within each OFDM block, and it may change independently from one OFDM block to another. The transmitted/received signals are differentially en/decoded in the frequency dimension within each OFDM block. The performance of the proposed scheme depends on the Channel power delay profile. Moreover, if the statistics of the power delay profile are known at the transmitter, we further propose to permutate the Channel frequency responses over subcarriers; by using Dijkstra's algorithm to increase the performance of the DSFM scheme. Simulation results show that the DSFM scheme with permutations performs very well for various Channel profiles.
S S Hemami - One of the best experts on this subject based on the ideXlab platform.
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distortion optimized multiple Channel image transmission under delay constraints
International Conference on Acoustics Speech and Signal Processing, 2004Co-Authors: S S HemamiAbstract:When multiple Channels are aggregated into a higher bandwidth Logical Channel, strategic product codes can be used to protect data against both Channel losses and failures. Previous work in (W. Xu et al., Proc. ICME, vol.1, p.285-288, 2003) has considered a delay-optimal partitioning scheme given pre-determined error correction codes (ECCs). In order to achieve an improved distortion performance, image bit streams can be partitioned together with an appropriate selection of ECCs based on Channel conditions. This paper addresses the problem of jointly partitioning image data over multiple Channels and selecting product coding rates from a finite set to minimize the decoding distortion under delay constraints. Experimental results show that the image quality degrades very slightly when the delay constraint decreases over a wide range, with a gain up to 4.5 dB achieved over that using a sequential optimization method.
Hwang-cheng Wang - One of the best experts on this subject based on the ideXlab platform.
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On Demand Resource Allocation for LTE Uplink Transmission Based on Logical Channel Groups
Mobile Networks and Applications, 2017Co-Authors: Kuo-chang Ting, Hwang-cheng Wang, Chih-cheng TsengAbstract:It is a hard task to allocate wireless resources for uplink transmission in LTE system. The main goals of previous research aimed at maximizing system throughput or fairness among UEs, while the real requirements of UEs were not considered. The result is that Resource Blocks (RBs) allocated by eNB are usually wasted and the requirements of UEs are not satisfied. We proposed an AAG-2 scheduling scheme, which can ensure the QoS of Guaranteed Bit Rate (GBR) bearers and at the same time efficiently allocate RBs to non-GBR bearers so as to improve resource utilization. In order to facilitate the management of bearers, the 3GPP (3rd Generation Partnership Project) suggested dividing bearers into four Logical Channel Groups (LCGs), rather than just GBR and non-GBR bearers. So far, 3GPP has not specified the mapping between LCGs and bearers of different QoS Class Identifiers (QCIs), but leaves the decision to system operators. In this paper, we propose a new scheme, AAG-LCG, wherein bearers are classified into four LCGs with different priority levels. With the proposed scheme, eNB can efficiently allocate RBs to meet the QoS requirements of various LCG bearers while maintaining sound overall system performance.
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resource allocation scheme for lte uplink transmission based on Logical Channel groups
Quality Reliability Security and Robustness in Heterogeneous Networks. 12th International Conference QShine 2016 Seoul Korea July 7–8 2016 Proceedings, 2017Co-Authors: Fangchang Kuo, Kuo-chang Ting, Chih-cheng Tseng, Hwang-cheng WangAbstract:It is still a difficult problem to allocate wireless resources for uplink transmission in LTE system. The main goals of previous researches aim at maximizing system throughput or fairness among UEs. However, the real requirements of UEs are not considered. The result is that Resource Blocks (RB) allocated by eNB are usually wasted and the requirements of UEs are not satisfied. We presented an AAG-2 scheduling scheme, which can ensure the QoS of GBR bearers, while at the same time efficiently distributes RBs to non-GBR bearers so as to improve resource utilization. However, in order to facilitate the management for many bearers, 3GPP suggested divide bearers into four Logical Channel Groups (LCG), rather than only two kinds of bearers mentioned above. So far, 3GPP has not specified how to map between LCG and bearers of different QoS Class Identifiers (QCIs), but left it to the operator for customization. As a result, it is an important issue about how to group bearers and how to guarantee QoS, while make good use of free RB. In this paper, we propose a new-version of AAG-2, named AAG-LCG, where bearers are classified into four LCGs with different priority levels. Especially, with the proposed scheme, eNB can efficiently allocate RBs to meet the QoS requirements of different LCG bearers, while also maintain sound overall system performance.
Chih-cheng Tseng - One of the best experts on this subject based on the ideXlab platform.
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On Demand Resource Allocation for LTE Uplink Transmission Based on Logical Channel Groups
Mobile Networks and Applications, 2017Co-Authors: Kuo-chang Ting, Hwang-cheng Wang, Chih-cheng TsengAbstract:It is a hard task to allocate wireless resources for uplink transmission in LTE system. The main goals of previous research aimed at maximizing system throughput or fairness among UEs, while the real requirements of UEs were not considered. The result is that Resource Blocks (RBs) allocated by eNB are usually wasted and the requirements of UEs are not satisfied. We proposed an AAG-2 scheduling scheme, which can ensure the QoS of Guaranteed Bit Rate (GBR) bearers and at the same time efficiently allocate RBs to non-GBR bearers so as to improve resource utilization. In order to facilitate the management of bearers, the 3GPP (3rd Generation Partnership Project) suggested dividing bearers into four Logical Channel Groups (LCGs), rather than just GBR and non-GBR bearers. So far, 3GPP has not specified the mapping between LCGs and bearers of different QoS Class Identifiers (QCIs), but leaves the decision to system operators. In this paper, we propose a new scheme, AAG-LCG, wherein bearers are classified into four LCGs with different priority levels. With the proposed scheme, eNB can efficiently allocate RBs to meet the QoS requirements of various LCG bearers while maintaining sound overall system performance.
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resource allocation scheme for lte uplink transmission based on Logical Channel groups
Quality Reliability Security and Robustness in Heterogeneous Networks. 12th International Conference QShine 2016 Seoul Korea July 7–8 2016 Proceedings, 2017Co-Authors: Fangchang Kuo, Kuo-chang Ting, Chih-cheng Tseng, Hwang-cheng WangAbstract:It is still a difficult problem to allocate wireless resources for uplink transmission in LTE system. The main goals of previous researches aim at maximizing system throughput or fairness among UEs. However, the real requirements of UEs are not considered. The result is that Resource Blocks (RB) allocated by eNB are usually wasted and the requirements of UEs are not satisfied. We presented an AAG-2 scheduling scheme, which can ensure the QoS of GBR bearers, while at the same time efficiently distributes RBs to non-GBR bearers so as to improve resource utilization. However, in order to facilitate the management for many bearers, 3GPP suggested divide bearers into four Logical Channel Groups (LCG), rather than only two kinds of bearers mentioned above. So far, 3GPP has not specified how to map between LCG and bearers of different QoS Class Identifiers (QCIs), but left it to the operator for customization. As a result, it is an important issue about how to group bearers and how to guarantee QoS, while make good use of free RB. In this paper, we propose a new-version of AAG-2, named AAG-LCG, where bearers are classified into four LCGs with different priority levels. Especially, with the proposed scheme, eNB can efficiently allocate RBs to meet the QoS requirements of different LCG bearers, while also maintain sound overall system performance.
Vaduvur Bharghavan - One of the best experts on this subject based on the ideXlab platform.
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a new model for packet scheduling in multihop wireless networks
ACM IEEE International Conference on Mobile Computing and Networking, 2000Co-Authors: Songwu Lu, Vaduvur BharghavanAbstract:The goal of packet scheduling disciplines is to achieve fair and maximum allocation of Channel bandwidth. However, these two criteria can potentially be in conflict in a generic-topology multihop wireless network where a single Logical Channel is shared among multiple contending flows and spatial reuse of the Channel bandwidth is possible. In this paper, we propose a new model for packet scheduling that addresses this conflict. The main results of this paper are the following: (a) a two-tier service model that provides a minimum “fair” allocation of the Channel bandwidth for each packet flow and additionally maximizes spatial reuse of bandwidth, (b) an ideal centralized packet scheduling algorithm that realizes the above service model, and (c) a practical distributed backoff-based Channel contention mechanism that approximates the ideal service within the framework of the CSMA/CA protocol.
