International Symposium on Wireless Communication Systems 

About: International Symposium on Wireless Communication Systems is an academic conference. The conference publishes majorly in the area(s): MIMO & Communication channel. Over the lifetime, 2677 publications have been published by the conference receiving 23566 citations.

Cache-enabled small cell networks: Modeling and tradeoffs

Abstract: We consider the problem of caching in next generation mobile cellular networks where small base stations (SBSs) are able to store their users' content and serve them accordingly. The SBSs are stochastically distributed over the plane and serve their users either from the local cache or internet via limited backhaul, depending on the availability of requested content. We model and characterize the outage probability and average content delivery rate as a function of the signal-to-interference-ratio (SINR), base station intensity, target file bitrate, storage size and file popularity. Our results provide key insights into the problem of cache-enabled small cell networks.

Uplink non-orthogonal multiple access for 5G wireless networks

Abstract: Orthogonal Frequency Division Multiple Access (OFDMA) as well as other orthogonal multiple access techniques fail to achieve the system capacity limit in the uplink due to the exclusivity in resource allocation. This issue is more prominent when fairness among the users is considered in the system. Current Non-Orthogonal Multiple Access (NOMA) techniques introduce redundancy by coding/spreading to facilitate the users' signals separation at the receiver, which degrade the system spectral efficiency. Hence, in order to achieve higher capacity, more efficient NOMA schemes need to be developed. In this paper, we propose a NOMA scheme for uplink that removes the resource allocation exclusivity and allows more than one user to share the same subcarrier without any coding/spreading redundancy. Joint processing is implemented at the receiver to detect the users' signals. However, to control the receiver complexity, an upper limit on the number of users per subcarrier needs to be imposed. In addition, a novel subcarrier and power allocation algorithm is proposed for the new NOMA scheme that maximizes the users' sum-rate. The link-level performance evaluation has shown that the proposed scheme achieves bit error rate close to the single-user case. Numerical results show that the proposed NOMA scheme can significantly improve the system performance in terms of spectral efficiency and fairness comparing to OFDMA.

Channel measurements for large antenna arrays

Abstract: Equipping base stations (BSs) with very large antenna arrays is a promising way to increase the spectral and energy efficiency of mobile communication systems without the need for new cell sites. However, the prominently theoretical works on this topic are based on several crucial assumptions about the wireless channel which have not been sufficiently validated by measurements. In this paper, we report on an outdoor measurement campaign with a scalable virtual antenna array consisting of up to 112 elements. The large amount of acquired data allows us to study several important aspects of large-scale MIMO systems. For example, we partially confirm the theoretical results based on uncorrelated channels which predict that the channels at different positions become more and more orthogonal as the number of antennas grows. However, for the measured channels, the marginal gain of an additional antenna quickly diminishes. Nevertheless, our results indicate that most of the theoretical benefits of large-scale MIMO could be realized also over the measured channels.

Performance of non-orthogonal access with SIC in cellular downlink using proportional fair-based resource allocation

Abstract: This paper investigates the system-level throughput of non-orthogonal access with a successive interference canceller (SIC) in the cellular downlink assuming proportional fair (PF)-based radio resource (bandwidth and transmission power) allocation. The purpose of this study is to examine the possibility of applying non-orthogonal access with a SIC to the systems beyond the 4G (thus IMT-Advanced) cellular system. Both the total and cell-edge average user throughput are important in a real system. PF-based scheduling is known to achieve a good tradeoff by maximizing the product of the average user throughput among users within a cell. In non-orthogonal access with a SIC, the scheduler allocates the same frequency to multiple users, which necessitates multiuser scheduling. To achieve a better tradeoff between the total and cell-edge average user throughput, we propose and compare three power allocation strategies among users, which are jointly implemented with multiuser scheduling. Extensive simulation results show that non-orthogonal access with a SIC with a moderate number of non-orthogonally multiplexed users significantly enhances the system-level throughput performance compared to orthogonal access, which is widely used in 3.9 and 4G mobile communication systems.

Genetic Algorithm to Optimize Node Placement and Configuration for WLAN Planning

Abstract: This paper presents a novel algorithm to rapidly create a high quality network plan for IEEE 802.11 based WLAN according to assigned design requirements. The algorithm uses a Genetic Algorithm (GA) to explore the design space, and a IEEE 802.11 rate adaptation aware QoS estimation functionality to provide feedback for the algorithm and for a network designer. The algorithm selects AP devices, locations, antennas, as well as AP configuration including transmission power and frequency channel. The algorithm was used in WLAN planning for a suburb, which is under development in Tampere-Lempaala area in Finland. Compared to manual network planning, the developed algorithm was able to create a network plan with 133 % capacity, 98 % coverage, and 93 % cost. Manually the corresponding network planning took hours, whereas the algorithm computation time was 15 minutes.