Hongyi Yu

Performance of dynamic CoMP cell selection in 3GPP LTE system level simulation

With the rapid progress of 3GPP LTE/LTE-As standardization, research about coordinate multi point reception / transmission (CoMP) is very popular. However, topics about CoMP were freezed in around 2009 by 3GPP, so further research and performance analysis about key techniques in CoMP is very little. In this paper, we studied the dynamic cell selection method which is presented in some proposals [1], and a performance analysis in system level is performed using our LTE system level simulator. A better algorithm of Dynamic coordinated multi-point Cell Selection is studied and suggested according to the simulation result.

Performance analysis of dynamic CoMP cell selection in LTE-advanced Heterogeneous Networks scenario

In the year 2011, process of standardization of 3GPP LTE release 11 has been performed. In order to help increase system spectrum efficiency and cell-edge user throughput, Heterogeneous Networks (HetNet) is introduced as an extension of CoMP. However, topics about HetNet CoMP are still blank and related proposals or performance analysis is still pending to be filled. In this paper, we extended the dynamic cell selection method which is presented in some proposals [1], and a performance analysis in system level is performed using our LTE-Advanced system level simulator. A better algorithm of Dynamic coordinated multi-point Cell Selection is studied and suggested according to the simulation result.

Performance analysis of the separation of uplink and downlink under LTE-Advanced system level simulation: An energy aware point of view

With the rapid development of wireless personal communications, demand for higher rates and bandwidth becomes more and more significant. In order to satisfy the need, network providers tried to deploy more and more access points such as the RRHs, which can effectively increase spectrum efficiency and ensure reliable QoS to users. In fact, demand for resources in uplink and downlink is not equal in many of the services, such as online movie, downloading, etc. So the separation of uplink and downlink is developed, which allows the heavy traffic for downlink can be served by RRHs and the light one for uplink can be directly served by traditional micro/macro cell. Traditional research of the heterogeneous networks of LTE-Advanced mainly focus on system performance. But in this paper, we studied the effect of the separation from an energy efficient point of view under the evaluation of the LTE-Advanced system level simulation. The design of signaling to implement the separation is firstly raised. The cost and performance of the separation are also evaluated and fully analyzed.

Energy efficient cooperative cell control of LTE-Advanced cellular networks

To reduce energy waste in future cellular networks, the most effective and reliable method is to close idle base stations when not needed, but how to find the proper and optimal method to control the target cell and the adjacent ones are still blank according to recent researches. In this work, we extend our research in cooperative scheme, and figure out a heuristic control method of eNodeBs in GREEN mode. We first define the energy efficient controls of LTE-Advanced cells in cooperative mode and raise a heuristic algorithm to support the on-off optimal control of LTE-Advanced cooperative eNodeBs, especially when and which eNodeB will be changed into sleep mode and which one(s) need to be waken up. Compared with no shut down methods, we have obtained about six times of the total savings by adopting our control method with the cost of less than 6% of the system overall QoS under both theoretical and LTE-Advanced system level simulation platform.

Energy efficient cooperative sleep control using small cell for wireless networks

The demand for higher throughput and more reliable quality of service (QoS) explosive increases the number of base stations in future wireless networks, which causes severe energy waste problems in wireless networks, especially when base stations are in low traffic load status. This paper has two main contributions: first of all, we propose a semistatic energy efficient method to find out the optimal on-off pattern considering the interference from adjacent base stations using integer convex optimization, from which the optimal on-off proportion of base stations could be obtained; then we propose a novel energy efficient cooperative heuristic algorithm in dynamic scenario, by separating the waiting time into two independent Markov processes using the new method; the total power consumption could be reduced significantly by adopting the novel method. Compared with reference method, simulation results indicate that in semistatic scenario, the total system power consumption could be reduced up to 26%, and, in dynamic scenario, the system power consumption could be reduced up to 40%.

Performance analysis of adaptive substream selection method in 3GPP LTE-Advanced system level simulation

In Release 11 of the LTE-Advanced specification, 8×8 transmission mode is raised to support higher transmission rate. But due to different channel conditions, spatial gain will not always increase with the increasement of antennas. How to make full use of spatial resources is a problem in LTE related areas. In this paper, an adaptive substream selection method is given which is used in 8×8 MIMO scenarios of 3GPP LTE-Advanced systems. Based on feedbacks of channel information (e.g. SRS in TDD system or Channel Estimation in FDD system), we can effectively predict the optimal stream mapping method at given timeslot. A system level simulation result is given to prove the effectiveness of our method under our Matlab-Based LTE-Advanced System Level Simulation platform.

Energy efficient content aware cache and forward operation in 3GPP LTE-Advanced base stations

Energy consumption problem in mobile personal communications recently becomes popular. Generally, the design and construction of mobile networks are appropriate for peak data traffic, so at leisure time and regions, base station resources will be wasted. Previous researches always tried to reduce the energy consumption of base stations, which takes up about 60% of the total consumption in WCDMA networks. In this work, we tried to focus on the consumption in core networks, which might be ignored in related researches. Considering the sociality of mobile users, plenty of users may concentrate on the same data such as hot news, videos, etc. Because the users with the same interest is huge, so the transmission from the source web server to mobile users of the same redundant data will cause unnecessary energy waste in core networks. In this paper, we design and analysis the method of adding a cache in the base stations, that will store some of the hot information. If the same hot information is needed, data will directly be sent from base stations cache instead of requiring from the content server to save the transmission energy of the core network. A system level simulation under LTE-Advanced Release 11 environment has been done to prove the effectiveness of our design using a simple probabilistic model. From the simulation result, our method can save up to 50% of the total energy consumption considering the consumption of LTE-Advanced core networks.

Energy efficient joint optimization of electric antenna tilt and transmit power in 3GPP LTE-Advanced: A system level result

Energy consumption problem gradually becomes serious with rapid demand of higher throughput and more reliable QoS. The operation that shut down idle base stations is effective to reduce network energy consumption as a conclusion. However, the shut down operation will cause the problem of losing coverage of system users. In order to maintain coverage after shut down base stations, operations of adjacent cells such as adjusting transmit power and changing antenna tilt are in great demand. In this work, we evaluate the performance of changing electric antenna tilt and transmit power after shutdown idle base stations. As an extension of our previous work, a novel ergodic method has been given and evaluation has been done under LTE-Advanced system level simulation platform. Contribution of this work can be summarized as follows: 1) we first evaluate and prove the necessity of changing antenna tilt and transmit power after shut down idle base stations; 2) we first quantize the system improvement under LTE-Advanced system level simulation using our novel method.

System level performance of energy efficient dynamic mechanical antenna tilt angle switching in LTE-Advanced systems

Energy consumption in current cellular communication systems becomes more and more critical with the demand for higher throughput and explosive growth of terminal equipment. However, the consumption is evitable in low traffic load time or area, e.g. in late-night. In order to reduce system energy consumption, power off low load base stations is an easy and effective way to reduce energy consumption, but lead to the problem of damaging the coverage performance. In this paper, we studied the effect of adjusting mechanical tilt angle and transmit power of base stations in an ergodic way after shut down adjacent idle base stations. Compared with traditional shutdown method, the changing of mechanical tilt and transmit power jointly can effectively help maintain coverage and lower system power consumption. Evaluation has been done under the LTE-Advanced system level simulation.

Energy aware optimal resource allocation in backhaul constraint wireless networks: a two base stations scenario

In future wireless communication systems, the capacity constrained backhaul gradually becomes bottleneck both in spectrum efficiency and energy efficiency, especially in joint processing of LTE-Advanced. This paper addresses the issue of energy aware resource allocation with limited backhaul capacity in uplink cooperative reception, where two base stations (BSs) equipped with single-antenna each serving multiple users with single-antenna via multicarrier are considered. We propose a novel energy efficient cooperative scheme based on compress-and-forward and user pairing to solve the problem in two base stations scenario. In order to maximize system throughput and increase energy efficiency under the limited backhaul capacity constraint, we formulate the joint optimization problem of user pairing, subcarrier mapping, and backhaul capacity sharing between different pairs (subcarriers). An energy efficient algorithm based on alternating optimization strategy and perfect mapping is proposed to solve this mixed integer programming problem. Simulations show that this allocation algorithm can improve the system capacity and energy efficiency significantly compared with the blind alternatives.