Physical layer security for multi-user MIMO visible light communication systems with generalized space shift keying

We consider the physical layer security (PLS) of multi-user (MU) multiple-input-multiple-output visible light communication (VLC) systems with an eavesdropper (Eve) and propose a novel spatial constellation design technique based on generalized space shift keying (MU-GSSK-SCD). The received signals of the legitimate users are optimized jointly, such that their bit error ratios (BERs) are minimized and Eve's BER is significantly degraded. The emission power of randomly selected light-emitting diodes is adjusted, by exploiting users' channel state information at the transmitter. Our strategy ensures that legitimate users receive confidential messages fully in an undistorted fashion, while any meaningful leakage to Eve is strongly prohibited, without any artificial noise addition. Every user can decode only its information, hence inter-user security is also guaranteed. The PLS improvements are presented in terms of both BERs and achievable secrecy rates in practical VLC scenarios. For various user configurations, it is shown that MU-GSSK-SCD increases the BER at Eve to the 0.5 level, while providing minimized BERs to the legitimate users. The achievable secrecy rate region is derived for MU-GSSK-SCD and it is shown that full secrecy can be achieved at 0 dB signal-to-noise ratio (SNR) level with a user separation as small as 90 cm

Energy harvesting cooperative multiple access under energy storage losses

Bu bildiride, enerji hasat eden iki vericiyle bir alıcının haberleştiği işbirlikli bir çoklu erişim kanalı için, sonlu batarya sığası ve enerji depolama kayıpları altında ulaşılabilir gönderim bölgesi eniyileme problemini çözüyoruz. İşbirliğinin gecikme kısıtlı ve gecikme toleranslı olduğu durumları ayrı ayrı ele alarak, her iki durumda eniyi iletim gücü ve hızı dağılımının batarya limitleri ve verimsizliğine göre değişimini inceliyoruz. Gecikme kısıtlı ve toleranslı durumların gönderim alanlarını bulup karşılaştırıyoruz.For a two-user cooperative multiple access channel with energy harvesting transmitters, we formulate and solve the achievable departure region maximization problem under finite battery capacities and energy storage losses. Treating delay constrained and delay tolerant cooperation scenarios separately, we investigate the dependence of the optimum transmission power and rate allocation policy on the battery limitations and storage inefficiencies. We obtain and compare the achievable departure regions for delay constrained and tolerant scenarios.Publisher's Versio

Cooperative Multiple Access under Energy Harvesting Constraints

We consider a cooperative multiple access channel (MAC) with two energy harvesting transmitters. The transmitters perform delay constrained transmission, i.e., every information block is encoded, transmitted and decoded between two consecutive energy harvests. We aim to maximize the achievable departure region over a finite transmission duration. We formulate the departure region maximization as a convex optimization problem. We propose an iterative algorithm which uses a directional waterfilling strategy to calculate the optimal power components. The departure region obtained by cooperation is shown to be significantly larger than that of a MAC without cooperation under the same energy arrival patterns. As a special case, we also analyze an energy harvesting relay channel with full duplex cooperation.Publisher's Versio

Delay tolerant cooperation in the energy harvesting multiple access channel

We consider the optimum transmit scheduling problem for a two user energy harvesting cooperative multiple access channel. We assume a slotted model where energy harvests in each slot are known a priori. We propose a delay tolerant cooperation model: the transmitters create common information in a given slot, but need not cooperatively send the created common information immediately; they may relegate all or part of the cooperative message transmission to upcoming slots. We propose a modified block Markov superposition coding scheme based on message re-partitioning, that spans multiple slots. We characterize the corresponding achievable departure region by a deadline, and maximize it subject to energy harvesting constraints. We show that, delay tolerant cooperation need not necessarily improve the departure region over delay constrained cooperation, and derive a sufficient condition for the equivalence of the two policies. We compare optimal delay constrained and delay tolerant cooperation policies, and their achievable departure regions via simulations.This work was supported by Tubitak Grant 113E556Publisher's Versio