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Performance gain can be obtained by dynamically reconfiguring the uplink and downlink radio frames in TDD systems. FDD systems can also benefit from the flexibility in the allocation of uplink and downlink resources. The paper proposes a specific implement of flexible duplex based on selection between different designs of radio frames to make the FDD network more adaptive to the real time situation...
Heterogeneous network (HetNet) where the macro cells are underlaid with low power node (LPN) has been introduced to HSPA+ to enhance the system performance in a cost-efficient way. But the Uplink and Downlink (UL-DL) mismatch issue caused by applying the heterogeneous deployment will inevitably limit the performance in both uplink and downlink HSPA+ system. To mitigate the UL-DL mismatch effect, E-DCH...
Small cell technology significantly improves the coverage and boosts the capacity in Heterogeneous Cellular Network. And Cell Range Expansion technology makes average rate nearly optimal in downlink. However, because of large transmit power disparities of different kinds of base stations, uplink and downlink need to be considered as two different networks. In uplink, the problem is that many user...
Heterogeneous network (HetNet) has been discussed earlier in LTE system. But recently, there also exist some studies concerning the standardization of HSPA HetNet. Interference coordination is still a critical topic in HSPA HetNet. Considering the network architecture of HSPA HetNet, in this paper, we develop a distributed interference coordination (DIC) scheme which involves power allocation and...
Antenna calibration to enhance the channel reciprocity between the uplink and downlink channels is necessary for the practical wireless system operating in the time division duplexing (TDD) mode. This paper investigates on the computation of the antenna calibration coefficients of the cooperative base stations' antennas in the network multiple-input and multiple-output (MIMO) system. An efficient...
Heterogeneous network (HetNet) has been studied earlier in the context of LTE. But lately, there are also some discussions about HetNet in HSPA. Cross-tier interference (CTI) is an annoying issue to be investigated in the co-channel HSPA HetNet (CHH) scenario. In this paper, we will focus on the downlink CTI problem in CHH and propose a solution to mitigate it. Our scheme involves the macro muting...
In traditional cellular networks, the capacity of downlink channels is limited by inter-cell interference (ICI). Basestation cooperation is a promising technique which yields large performance improvements by mitigating or eliminating ICI. However, many existing cooperation methods are far from practical due to intensive computational complexity. In this paper, we propose a practical method of base-station...
Device-to-Device (D2D) communication underlaying cellular networks can enhance the network capacity and spectrum efficiency when sharing cellular resources. However, the severe interference between D2D and cellular networks may lead to performance decrease of D2D and cellular communication. In this paper, we concentrate on suppressing the interference between D2D users and cellular networks when D2D...
Multi-user multi-input and multi-output based on block diagonalization algorithm can eliminate the multi-user interference, but in fact the existence of the non-ideal factors lead to the interference can not be cancelled completely. In this paper we study the performance of the 3GPP long term evolution system based on BD algorithm and propose a low complexity multi-user scheduling scheme to reduce...
Simulation of wireless communication system is usually divided into system-level and link-level. Link-level simulation is generally used to simulate the point-to-point physical layer technologies with propagation model taken into account, which means it is based on single-cell and single terminal scenario. Multi-cell model is not often studied in link-level mainly due to its high complexity. So we...
In practical use, data traffic has a feature of high-burst in wireless network, which means that the serve request of a user is not continuous. With full buffer traffic model, network operators can give evaluations on the peak data rate and the least data rate of heavy load network. However, rather than the peak data rate and the least data rate, what attracts users most may sometimes be the typical...
In this paper, we consider practical multiuser multiple-input multiple-output (MU-MIMO) systems where each user has multiple receive antennas and limited channel feedback is available at the base station (BS). The joint combiner and precoding scheme for downlink transmission is proposed, in which we consider the joint use of the receive antenna combiner at each user and precoding at the BS. In the...
In this paper, we propose a new efficient distributed dynamic resource allocation (DDRA) scheme to coordinate the inter-cell interference and verify the existence of the Nash equilibrium. This new scheme can be utilized in the long term evolution (LTE) uplink and downlink scenarios to mitigate the inter-cell interference effectively. The system level simulations show that the system performance is...
Deployment of heterogeneous networks is one of the key technologies in LTE-Advanced. After low-power nodes were introduced to cellular system, great changes have taken place in the structure of traditional networks. Thus, range expansion (RE) scheme is proposed to adapt to these changes in the standardization process of heterogeneous networks. This paper studies the performance of heterogeneous networks...
Block diagonalization (BD) algorithm is an efficient precoding technique for multiuser multiple-input multiple-output (MU-MIMO) system. In previous researches, BD precoding was mostly realized based on the singular value decomposition (SVD). However, in the cooperative transmission scenario where the dimension of channel matrix is significantly enlarged compared with the single base station (BS) transmission...
Abstract-Single and Multi-layer adaptive eigen based beamforming (EBB) has been proved to be a promising method to achieve the tradeoff between diversity and spatial multiplexing. But the CQI in multi-layer mode is calculated according to the CQI in single-layer mode. Lack of accurate multi-layer CQI will induce performance loss when implementing layer adaptation at eNodeB. In this paper, aiming to...
In real environments, channel reciprocity cannot be directly exploited between uplink and downlink in time-division duplex (TDD) due to antenna gain mismatch. Previous work about antenna calibration mainly focused on single cell. This work proposes an adaptive scheme for antenna calibration between two cooperative BSs. The proposed scheme aims at achieving an equal ratio between antenna transmitter...
A cognitive radio (CR) system should have the ability to detect the presence of incumbent users and adjust its transmission so that it can utilize unused licensed spectrum without causing interference to incumbent users. To effectively protect incumbent users, properly modeling the expected interference from CR system is therefore very important. We model the accumulative interference generated from...
Antenna gain mismatch between transmitter and receiver circuits has been regarded as an obstacle for exploiting channel reciprocity between uplink and downlink channels in time-division duplex (TDD) multiple-input multiple-output (MIMO) systems. To the best knowledge of the authors, little work to date has been on about the impact of antenna mismatches on the precoding vector. Motivated by this fact,...
In this paper, we consider a joint power control and resource allocation scheme for co-channel deployed femtocells in macrocell networks. The strong interference in the downlink from the femtocells should be well controlled to satisfy the quality of service (QoS) requirement of both macrocell users and femtocell users. We provide both centralized and distributed schemes to solve the formulated optimization...
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