Spatial Reuse Of Radio Resources Research Articles

LTE-V2X Mode 3 scheduling based on adaptive spatial reuse of radio resources

LTE-V2X (also known as C-V2X or Cellular V2X) introduces direct or sidelink V2V (Vehicle to Vehicle) communications using the PC5 interface. LTE-V2X defines two modes (Mode 3 and Mode 4) for the management of radio resources. This study focuses on Mode 3 where the cellular network manages and allocates the radio resources for direct or sidelink V2V communications. Contrary to Mode 4, the 3GPP standards do not define any concrete scheduling scheme to allocate resources under Mode 3. In this context, this paper proposes a context-based scheduling scheme for LTE-V2X Mode 3 that exploits the geographical location of vehicles and dynamically configures its operation with the objective that all vehicles experience a similar level of interference when resources must be shared. The proposed scheduling scheme, referred to as DIRAC (aDaptive spatIal Reuse of rAdio resourCes), is validated analytically and its performance is evaluated through system level simulations. The evaluation shows that DIRAC outperforms existing LTE-V2X Mode 3 and Mode 4 scheduling schemes and ensures a more scalable and stable network operation as the channel load and congestion increases.

Resource Allocation in Highly Dynamic Device-to-Device Communication: An Adaptive Set Multi-Cover Approach

Device-to-device (D2D) communication has recently gained much attention for its potential to boost the capacity of cellular systems. D2D enables direct communication between devices while bypassing a base station (BS), hence decreasing the load of BSs and increasing the network throughput via spatial reuse of radio resources. However, the cellular system is highly dynamic, an optimal allocation plan of radio resource to D2D links at one time point can easily become suboptimal when devices move. Thus, to maximize spatial reuse in cellular systems, it is crucial to update the resource allocation adaptively to reflect the current system status. In this paper, we develop the first adaptive solution framework to the dynamic resource problem for maximizing spatial reuse. At the core of the framework, we present the two algorithms for the adaptive set multicover problem with approximation ratio f and log n, respectively, where f is the frequency of the most frequent element and n is the total number of elements. The experimental results not only show that our solutions have a significant improvement in running time, compared with optimal or approximated offline methods, but also demonstrate their good performance through the resource usage, network throughput, and other metrics.

Analytical performance estimation of network‐assisted D2D communications in urban scenarios with rectangular cells

AbstractThe aggressive spatial reuse of radio resources is considered today as one of the most promising avenues to achieve significant cellular capacity improvements in future fifth‐generation networks. Accordingly, device‐to‐device (D2D) communications are an emerging paradigm that promises to offer these much expected gains without the need for additional investments into the network infrastructure. However, before this attractive technology can be deployed ubiquitously, the research community has to fully understand the extent of its potential performance benefits across typical scenarios of interest. In this work, we consider one such use case of rectangular cells (common for offices, shopping malls, dormitories, etc.) and develop the corresponding analytical methodology for D2D performance evaluation. As our target metric, we employ the signal‐to‐interference (SIR) ratio experienced by a D2D user. To this end, we propose two relatively simple approximations for SIR distribution and hence capture the related parameters, including user throughput. Further, we carefully investigate the most interesting numerical results by making important conclusions on the envisioned operation of our chosen scenario. In particular, we demonstrate that under certain conditions, the SIR behaviour is insensitive to the dimensions of cells, while different propagation exponents ‘scale’ its density function thus allowing to simplify the characterisation of SIR in a wide range of input parameters. Copyright © 2015 John Wiley & Sons, Ltd.

Two-Stage Semi-Distributed Resource Management for Device-to-Device Communication in Cellular Networks

In cellular networks, the device-to-device (D2D) communication increases the network capacity by spatial reuse of radio resources and prolongs the battery life of devices by reducing the transmission power. In this paper, we propose a two-stage semi-distributed resource management framework for the D2D communication. At the first stage of the framework, the base station (BS) allocates resource blocks (RBs) to BS-to-user device (B2D) links and D2D links, in a centralized manner. At the second stage, the BS schedules the transmission using the RBs allocated to B2D links, while the primary user device of each D2D link carries out link adaptation on the RBs allocated to the D2D link, in a distributed fashion. The proposed framework has the advantages of both centralized and distributed design approaches, i.e., high network capacity and low control/computational overhead, respectively. We formulate the problems of RB allocation to maximize the radio resources efficiency, taking account of two different policies on the spatial reuse of RBs. To solve these problems, we suggest a greedy algorithm and a column generation-based algorithm. By simulation, it is shown that the proposed scheme achieves the near-optimal performance while reducing the control/computational overhead.

Swarming Algorithms for Distributed Radio Resource Allocation: A Further Step in the Direction of an Ever-Deeper Synergism Between Biological Mathematical Modeling and Signal Processing

The major challenge faced by modern communication systems is the striking contrast between the ever-increasing demand for higher data rate links with guaranteed quality of service (QoS), on the one hand, and the scarcity of the radio resources, on the other hand. The solution of this dilemma is the increase of spectral efficiency. Several tools are available for improving spectral efficiency, like adaptive modulation and coding; multiple input, multiple output (MIMO) communications; cooperative multipoint communications; etc. Among all these tools, it is widely recognized that the approach having the potential for bringing the most significant improvement is spatial reuse of radio resources [1]. This calls for the deployment of base stations covering small cells of radius in the order of a few tens of meters. However, a dense deployment of conventional base stations is impractical because of the high costs of installation and maintenance. The way to overcome this limitation consists of the deployment of heterogeneous networks, which are composed of conventional base stations coexisting with low-cost base stations having very small transmit power and limited complexity. An example is given by femtocell networks [2], where femto access points, also called home enhanced node B, are installed indoors and cover cells of radius in the order of tens of meters. They avoid the wall penetration losses occurring in outdoor-to-indoor communications and are perfectly compliant with cellular standards. Consequently, they allow a significant traffic offload from the wireless to the wired channels, thus freeing important radio resources. This is a win-win strategy for operators and users: The operators get the capability of having more wireless traffic within a given area, thus increasing revenues; the users have a seamless connectivity to the network, with better QoS with respect to standard Wi-Fi and easier hand off. However, this solution does not come without technical challenges, the most important being interference management. In fact, while in conventional networks radio resource allocation is typically performed by the base stations, using a centralized approach, in the heterogeneous scenario, it becomes quite problematic to envisage a centralized approach taking into account both conventional and innovative base stations. The major limitation concerning the home base stations is that they have low complexity and, being owned by the users, they are not necessarily installed according to a radio optimization criterion and they may be switched on and off at the user?s will. Given this context, the only viable mechanism is to endow the network with some sort of self-organization capability, with a particular attention to keep interference under control. Self-organization can come in different forms: self-configuration, self-optimization, self-healing, etc. In particular, since some of the nodes have limited complexity and computational capabilities, it is fundamental to devise mechanisms such that the overall network is robust, as a whole, against abrupt and unpredictable changes of network conditions, like interference, change of connectivity, and so on, even if the individual nodes are not sophisticated enough to handle the problem appropriately. In fact, self-organization features are already introduced in the current standardization process of the 3rd Generation Partnership Project long-term evolution leading towards fourth-generation mobile communication systems [3].