arXiv subjects

Chuang Zhang

Publications and source records attributed to Chuang Zhang.

97 records · Page 6Linked to original sources

arXiv2014

Wireless Information and Energy Transfer for Two-Hop Non-Regenerative MIMO-OFDM Relay Networks

This paper investigates the simultaneous wireless information and energy transfer for the non-regenerative multipleinput multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM) relaying system. By considering two practical receiver architectures, we present two protocols, time switchingbased relaying (TSR) and power splitting-based relaying (PSR). To explore the system performance limit, we formulate two optimization problems to maximize the end-to-end achievable information rate with the full channel state information (CSI) assumption. Since both problems are non-convex and have no known solution method, we firstly derive some explicit results by theoretical analysis and then design effective algorithms for them. Numerical results show that the performances of both protocols are greatly affected by the relay position. Specifically, PSR and TSR show very different behaviors to the variation of relay position. The achievable information rate of PSR monotonically decreases when the relay moves from the source towards the destination, but for TSR, the performance is relatively worse when the relay is placed in the middle of the source and the destination. This is the first time to observe such a phenomenon. In addition, it is also shown that PSR always outperforms TSR in such a MIMO-OFDM relaying system. Moreover, the effect of the number of antennas and the number of subcarriers are also discussed.

cs.IT↗

arXiv2014

Downlink Resource Allocation for the High-speed Train and Local Users in OFDMA Systems

We consider providing services for passengers in a high-speed train and local users (quasi-static users) in a single OFDMA system. For the train, we apply a two-hop architecture, under which, passengers communicate with base stations (BSs) via a mobile relay (MR) installed in the train cabin. With this architecture, all passengers in the train can be represented by the MR. Since the channels of the MR and local users vary differently, we consider allocating system resources (power and subcarriers) over two time-scales for them. We formulate the problem as a capacity optimization problem for the MR subject to the sum capacity constraint of local users. We treat the inter-carrier interference (ICI) at the MR as additive Gaussian noise and derive an explicit expression for the ICI using the two-path Doppler spread model. Then we discuss the optimization problem and propose an optimal power and subcarrier allocation (OPSA) policy. The capacity obtained using OPSA is compared with that of constant power and subcarrier allocation (CPSA) policies. Simulation results justify the optimality of the OPSA. Besides, by comparing the capacity bounds achieved by OPSA with and without ICI, we find that only in specific regions, where the gap between the capacity bounds is large, do practical ICI cancellation methods provide meaningful rate gain.

cs.IT↗

arXiv2013

Service based hight-speed railway base station arrangement

To provide stable and high data rate wireless access for passengers in the train, it is necessary to properly deploy base stations along the railway. We consider this issue from the perspective of service, which is defined as the integral of the time-varying instantaneous channel capacity. With large-scale fading assumption, it will be shown that the total service of each base station is inversely proportional to the velocity of the train. Besides, we find that if the ratio of the service provided by a base station in its service region to its total service is given, the base station interval (i.e. the distance between two adjacent base stations) is a constant regardless of the velocity of the train. On the other hand, if a certain amount of service is required, the interval will increase with the velocity of the train. The above results apply not only to simple curve rails, like line rail and arc rail, but also to any irregular curve rail, provided that the train is travelling at a constant velocity. Furthermore, the new developed results are applied to analyze the on-off transmission strategy of base stations.

cs.IT↗

arXiv2013

Channel Service Based High Speed Railway Base Station Arrangement

With the rapid development of high-speed railways, demands on high mobility wireless communication increase greatly. To provide stable and high data rate wireless access for users in the train, it is necessary to properly deploy base stations along the railway. In this paper, we consider this issue from the perspective of channel service which is defined as the integral of the time-varying instantaneous channel capacity. It will show that the total service quantity of each base station is a constant. In order to keep high service efficiency of the railway communication system with multiple base stations along the railway, we need to use the time division to schedule the multiple stations and allow one base station to work when the train is running close to it. In this way, we find a fact that if the ratio of the service quantity provided by each station to its total service quantity is given, the base station interval(i.e. the distance between two adjacent base stations) is a constant, regardless of the speed of the train. On the other hand, interval between two neighboring base stations will increase with the speed of the train. Furthermore, using the concept of channel service, we also analyze the transmission strategy of base stations.

cs.IT↗

arXiv2013

Every-user delay guarantee for wireless multiple access systems

The quality of service (QoS) requirements are usually different from user to user in a multiaccess system, and it is necessary to take the different requirements into account when allocating the shared resources of the system. In this paper, we consider one QoS criterion--delay in a multiaccess system, and we combine information theory and queueing theory in an attempt to analyze whether a multiaccess system can meet the different delay requirements of users. For users with the same transmission power, we prove that only $N$ inequalities are necessary for the checking, and for users with different transmission powers, we provide a polynomial-time algorithm for such a decision. In cases where the system cannot satisfy the delay requirements of all users, we prove that as long as the sum power is larger than a threshold, there is always an approach to adjust the transmission power of each user to make the system delay feasible if power reallocation is available.

cs.IT↗

arXiv2003

Lorentz Force Correction and Radiation Frequency Property of Charged Particles in Magnetic Dipole

By concern of compression of charge density field, the corrected Lorentz force formula and consequent inference is presented. And further radiation frequency property of an individual charge density field in magnetic dipole is analyzed respectively for radiant property of the charged particle and the emitted electromagnetic wave transfer property between the moving radiant source and observer. As results, the behavior and radiation frequency property of the electron beam in magnetic dipole is interpreted upon the individual's behavior and property. At final, the potential application is put forward for wider interest.

physics.acc-ph↗

arXiv2003

Energy Differential Structure and Exchange of A Micro Flux Increment of Charged Particles in Longitudinal Acceleration

Differential energy structure of a micro multi-charged-particle system and the beam internal potential energy is derived with consequent property and ecessary inference. Then by combining the energy differential structure with differential transfer relations of physical flux density between different time domains, we present a general explicit formula for energy exchange in the beam element's transfer or accelerating process between source and observer, further give an analysis on relativistic beam's mass-energy relation and beam's energy up limits for resonant frequency (rf) and DC acceleration. Finally we discuss the property of elementary charge density field and consequences.

physics.acc-ph↗