Non-symmetric multi-antenna coded caching for location-dependent content delivery

Abstract Immersive viewing, as the next-generation interface for human-computer interaction, is emerging as a wireless application. A genuinely wireless immersive experience necessitates immense data delivery with ultra-low latency, raising stringent requirements for future wireless networks. In this regard, efficient usage of in-device storage and computation capabilities is a potential candidate for addressing these requirements. In addition, recent advancement in multi-antenna transmission has significantly enhanced wireless communication. Hence, this paper proposes a novel location-based multi-antenna coded cache placement and delivery scheme. We first formulate a linear programming cache allocation problem to provide a uniform quality of experience in different network locations; then, cache-placement is done for each location independently. Subsequently, based on the users’ spatial realizations, a transmission vector is created considering diverse available memory at each user. Moreover, a weighted-max-min optimization is used for the beamformers to support different transmission rates. Finally, numerical results are used to show the performance of the proposed scheme

Complexity reduction in multicast beamforming for D2D assisted coded caching

Abstract A novel D2D aided beamforming scheme is proposed, where the local cache content exchange among nearby users is exploited. The transmission phase is split into two sub-phases: local D2D content exchange and downlink transmission. In the D2D sub-phase, users can autonomously share content with the adjacent users. In the downlink sub-phase, the Base station (BS) simultaneously serves some number of users to fulfill their remaining content requests by utilizing multicast beamforming. We first explain the main procedure via two simple examples and show the complexity involved in beamformer design. Then, we present the general formulation and detailed complexity analysis. We show analytically that, by exploiting the D2D exchange, the complexity of downlink multicast beamformer design can be greatly decreased. This provides significantly enhanced overall content delivery performance in terms of computational complexity and total delivery time

Low-subpacketization multi-antenna coded caching for dynamic networks

Abstract Multi-antenna coded caching combines a global caching gain, proportional to the total cache size in the network, with an additional spatial multiplexing gain that stems from multiple transmitting antennas. However, classic centralized coded caching schemes are not suitable for dynamic networks as they require prior knowledge of the number of users to indicate what data should be cached at each user during the placement phase. On the other hand, fully decentralized schemes provide comparable gains to their centralized counterparts only when the number of users is very large. In this paper, we propose a novel multi-antenna coded caching scheme for dynamic networks, where instead of defining individual cache contents, we associate users with a limited set of predefined caching profiles. Then, during the delivery phase, we aim at achieving a combined caching and spatial multiplexing gain, comparable to a large extent with the ideal case of fully centralized schemes. The resulting scheme imposes small subpacketization and beamforming overheads, is robust under dynamic network conditions, and incurs small finite-SNR performance loss compared with centralized schemes

Non-symmetric coded caching for location-dependent content delivery

Abstract Immersive viewing is emerging as the next interface evolution for human-computer interaction. A truly wireless immersive application necessitates immense data delivery with ultra-low latency, raising stringent requirements for next-generation wireless networks. A potential solution for addressing these requirements is through the efficient usage of in-device storage and computation capabilities. This paper proposes a novel location-based coded cache placement and delivery scheme, which leverages the nested code modulation (NCM) to enable multi-rate multicasting transmission. To provide a uniform quality of experience in different network locations, we formulate a linear programming cache allocation problem. Next, based on the users’ spatial realizations, we adopt an NCM based coded delivery algorithm to efficiently serve a distinct group of users during each transmission. Numerical results demonstrate that the proposed location-based delivery method significantly increases transmission efficiency compared to state of the art

Low-complexity multicast beamforming for multi-stream multi-group communications

Abstract In this paper, assuming multi-antenna transmitter and receivers, we consider a multicast beamformer design for the weighted max-min-fairness (WMMF) problem in a multi-stream multi-group communication setup. Unlike the single-stream scenario, the WMMF objective in this setup is not equivalent to maximizing the minimum weighted SINR due to the summation over the rates of multiple streams. Therefore, the non-convex problem at hand is first approximated with a convex one and then solved using Karush-Kuhn-Tucker (KKT) conditions. Then, a practically appealing closed-form solution is derived for both transmit and receive beamformers as a function of dual variables. Finally, we use an iterative solution based on the sub-gradient method to solve for the mutually coupled and interdependent dual variables. The proposed solution does not rely on generic solvers and does not require any bisection loop for finding the achievable rate of various streams. As a result, it significantly outperforms the state-of-art in terms of computational cost and convergence speed

D2D assisted multi-antenna coded caching

Abstract A device-to-device (D2D) aided multi-antenna coded caching scheme is proposed to improve the average delivery rate and reduce the downlink (DL) beamforming complexity. Novel beamforming and resource allocation schemes are proposed where local data exchange among nearby users is exploited. The transmission is split into two phases: local D2D content exchange and DL transmission. In the D2D phase, subsets of users are selected to share content with the adjacent users directly. In this regard, a low complexity D2D mode selection algorithm is proposed to find the appropriate set of users for the D2D phase with comparable performance to the optimal exhaustive search. During the DL phase, the base station multicasts the remaining data requested by all the users. We identify scenarios and conditions where D2D transmission can reduce the delivery time. Furthermore, we demonstrate how adding the new D2D phase to the DL-only scenario can significantly reduce the beamformer design complexity in the DL phase. The results further highlight that by partly delivering requested data in the D2D phase, the transmission rate can be boosted due to more efficient use of resources during the subsequent DL phase. As a result, the overall content delivery performance is greatly enhanced, especially in the finite signal-to-noise (SNR) regime

D2D assisted beamforming for coded caching

Abstract Device-to-device (D2D) aided beamforming for coded caching is considered in a finite signal-to-noise ratio regime. A novel beamforming and resource allocation scheme is proposed where the local cache content exchange among nearby users is exploited. The transmission is split into two phases: local D2D content exchange and downlink transmission. In the D2D phase, users can autonomously share content with the adjacent users. The downlink phase utilizes multicast beamforming to simultaneously serve all users to fulfill the remaining content requests. A low complexity D2D-multicast mode selection algorithm is proposed with comparable performance to the optimal exhaustive search. We first explain the main procedure via one simple example and then present the general formulation. Furthermore, D2D transmission scenarios and conditions useful for minimizing the overall delivery time are identified. By exploiting the direct D2D exchange of file fragments, the common multicasting rate for delivering the remaining file fragments in the downlink phase is increased, providing greatly enhanced overall content delivery performance