LTE Advanced

About: LTE Advanced is a research topic. Over the lifetime, 4055 publications have been published within this topic receiving 74262 citations. The topic is also known as: Long-Term Evolution Advanced & LTE-A.

Carrier aggregation for LTE-advanced: uplink multiple access and transmission enhancement features

Abstract: Multiple access and transmission enhancement in support of carrier aggregation techniques has been actively studied in the 3GPP LTEAdvanced standardization process of the nextgeneration mobile broadband communication systems. By means of carrier aggregation, users can access a total bandwidth of up to 100 MHz in order to meet the IMT-Advanced requirements. This article first introduces and compares several uplink multiple access schemes in LTE-Advanced standard. Technical challenges arising from the use of carrier aggregation is then addressed, with focus on reference signals design for uplink transmission. Meanwhile, various candidate options are summarized and compared in terms of their system performance, computational complexity, and design flexibility. The article further proceeds to investigate the link performance with carrier aggregation, taking into account the presence of frequency offset and fast fading in the uplink channel. Numerical results are also presented, which indicate that advanced signal processing algorithms should be further studied and optimized to ensure reliable operation of the 3GPP LTE-Advanced in high mobility.

Equivalent Capacity in Carrier Aggregation-Based LTE-A Systems: A Probabilistic Analysis

Abstract: In this paper, we analyze the user accommodation capabilities of LTE-A systems with carrier aggregation for the LTE users and LTE-A users, respectively. The adopted performance metric is equivalent capacity (EC), defined as the maximum number of users allowed in the system given the user QoS requirements. Specifically, both LTE and LTE-A users are divided into heterogeneous user classes with different QoS requirements, traffic characteristics and bandwidth weights. Two bandwidth allocation strategies are studied, i.e., the fixed-weight strategy and the cognitive-weight strategy, where the bandwidth weights of different user classes are prefixed under the former and dynamically changing with the cell load conditions under the latter. For each strategy, closed-form expressions of ECs of different user classes are derived for LTE and LTE-A users, respectively. A net-profit-maximization problem is further formulated to discuss the tradeoff among the bandwidth weights. Extensive simulations are conducted to corroborate our analytical results, and demonstrate an interesting discovery that only a slightly higher spectrum utilization of LTE-A users than LTE users can result in a significant EC gain when the user traffic is bursty. Moreover, the cognitive-weight strategy is shown to outperform considerably the fixed-weight one due to stronger adaptability to the cell load conditions.

Dynamic Joint Resource Optimization for LTE-Advanced Relay Networks

Abstract: A dynamic optimization algorithm is proposed for the joint allocation of subframes, resource blocks, and power in the Type 1 inband relaying scheme mandatory in the LTE-Advanced standard. Following the general framework of Lyapunov optimization, we decompose the original problem into three sub-problems in the forms of convex programming, linear programming, and mixed-integer programming. We solve the last sub-problem in the Lagrange dual domain, showing that it has zero duality gap, and that a primal optimum can be obtained with probability one. The proposed algorithm dynamically adapts to traffic and channel fluctuations, it accommodates both instantaneous and average power constraints, and it obtains arbitrarily near-optimal sum utility of each user's average throughput. Simulation results demonstrate that the joint optimum can significantly outperform suboptimal alternatives.