Wireless communications technology continues to change and yield new standards for satisfying the user demands. As a result, multiple standards coexist and wireless communications systems supporting different air interfaces cannot interact with one another. Software-defined radio is regarded as the most promising solution to cope with this problem. In this paper, we discuss the design considerations of SDR systems from a base station point of view and propose new architecture which meets the inherent requirements of SDR platform. We then introduce hardware/software of SDR platform we accomplished on the basis of the new architecture. In addition, the results of basic transmission and receiving performance are presented to prove the feasibility of the proposed platform as a base station.

In real-time multimedia processing systems a very large part of the power consumption is due to the data storage and data transfer. Moreover, the area cost is often largely dominated by the memory modules. In deriving an optimized (for area and/or power) memory architecture, memory size computation is an important step in the exploration of the possible algorithmic specifications of multimedia applications. This paper presents a novel non-scalar approach for computing exactly the memory size in real-time multimedia algorithms. This methodology uses both algebraic techniques specific to the data-flow analysis used in modern compilers and, also, more recent advances in the theory of polyhedra. In contrast with all the previous works which are only estimation methods, this approach performs exact memory computations even for applications significantly large in terms of the code size, number of scalars, and number of array references.

In this letter, efficient two-dimensional (2-D) fast algorithms for realizations of 88 forward and inverse integer transforms in H.264/AVC fidelity range extensions (FRExt) are proposed. Based on matrix factorizations with Kronecker product and direct sum operations, efficient fast 2-D 88 forward and inverse integer transforms can be derived from the one-dimensional (1-D) fast 88 forward and inverse integer transforms through matrix operations. The proposed fast 2-D 88 forward and inverse integer transform designs don't require transpose memory in hardware realizations. The fast 2-D 88 integer transforms require fewer latency delays and provide a larger throughput rate than the row-column based method. With regular modularity, the proposed fast algorithms are suitable for VLSI implementations to achieve H.264/AVC FRExt high-profile signal processing.

This paper presents a structural approach for synthesizing arbitrary multi-output multi-stage static CMOS circuits at the transistor level, targeting the reduction of transistor counts. To make the problem tractable, the solution space is restricted to the circuit structures which can be obtained by performing algebraic transformations on an arbitrary prime-and-irredundant two-level circuit. The proposed algorithm is guaranteed to find the optimal solution within the solution space. The circuit structures are implicitly enumerated via structural transformations on a single graph structure, then a dynamic-programming based algorithm efficiently finds the minimum solution among them. Experimental results on a benchmark suite targeting standard cell implementations demonstrate the feasibility and effectiveness of the proposed approach. We also demonstrated the efficiency of the proposed algorithm by a numerical analysis on randomly-generated problems.

Cooperative diversity represents an effective way of combating multipath fading through inter-terminal cooperation in wireless networks. In this letter, we propose a new participation strategy that increases the chance of cooperation and present the closed-form expression for outage probability. Numerical results demonstrate that new participation strategy improves the outage performance.

In this letter, it is shown that a MAP detector can be employed with differential pulse-position modulation (L-DPPM) in an indoor optical wireless system. The MAP detector error performance is evaluated and compared with that of a hard-decision detector and MLSD over an intersymbol interference channel. It is shown that a MAP detector provides superb performance even in a dispersive channel with high DT.

An enhanced Ultra Wideband (UWB) signaling scheme that employs PSWF (Prolate Spheroidal Wave Functions)-based orthogonal chip pulses and ternary complementary code sets is proposed for Direct-Sequence (DS) UWB systems. Every information bit of each user is modulated and transmitted over a set of parallel sequences of PSWF-based orthogonal chip pulses and are further assigned to a ternary complementary code set with additional zero padding if necessary. Moreover, the ternary complementary code sets are generated to be mutually orthogonal and assigned to any pair of multiple users. Hence, the mitigation of multipath interference as well as multiple user interference (MUI) can be expected. Furthermore, the ternary code length can be greatly shortened by taking advantage of pulse and code orthogonality. Thus, the proposed transmission scheme is especially suitable for high data rate DS-UWB systems that offer very high flexibility.

An analytic approach for the generation of non-periodic and periodic complementary sequences is advanced for lengths that are powers of two. The periodic complementary sequences can be obtained using symmetric or anti-symmetric extensions. The properties of their autocorrelation functions are studied. The non-periodic complementary sequences are the intersection between anti-symmetric and symmetric periodic sequences. These non-periodic and periodic complementary sequences are identified to be special cases of non-periodic and periodic (or cyclic) orthogonal wavelet transforms. This relationship leads to the novel approach.

This paper considers systems consisting of communicating processes which can move between specified locations. Mobile telephone systems and intelligent transport systems are examples of them. The processes can exchange data as well as channels (e.g. frequencies) to be used in further communication. It may happen that two processes (e.g. telephones or cars) in different locations could communicate directly because they share a communication channel, but they cannot as there is a physical obstacle between the locations. A possible solution is to allow one process to send a message to another one through other processes and locations. To see if this is possible, a notion of connectivity of processes has been devised in the literature. A process was defined to be connectable to another one if a message from the first one could reach the other one by using any existing communication actions, allowed locations, and process moves in the system. A process-algebraic approach for checking connectivity was proposed. In this paper, it is shown how the temporal logic of actions (TLA) can be employed for the same purpose. In both approaches, connectivity of a process with another one is basically checked as follows. The first process includes a marking message in all its sending actions. Every process that receives this message gets marked and includes it in its own sending actions. The first process is connectable to the second one if there exists such a system execution sequence that the latter gets marked in it. Since TLA is a linear-time temporal logic, it can generally not express such a property. This paper, however, shows that it can be expressed and verified for a given TLA system specification. It also shows how to specify the marking operations and provides an example of connectivity checking.

For mobile visual communications, the development of more robust and efficient video traffic control and transmission techniques remains one of the most important issues. Foveated video originates from visual entropy reduction by removing undetectable high visual frequencies that occur at a distance from the fixation point. In this paper, compression gain is defined and measured to quantify the enhanced performance when the visual throughput of the regions of interest (ROI) is increased over a capacity-limited channel.

A new fast and reliable image objective quality evaluation technique is presented in this paper. The proposed method takes image structure into account and uses a low complexity homogeneity measure to evaluate the intensity uniformity of a local region based on high-pass operators. We experimented with monochrome images under different types of distortions. Experimental results indicate that the proposed method provides better consistency with the perceived image quality. It is suitable for real applications to control the processed image quality.

Receiver enhancement at mobile terminals such as using receiver diversity is a way of achieving greater downlink capacity. The enhancement, however, is achieved not instantaneously by a network operator but gradually by the individual users that choose and purchase their own mobile terminals. We investigate in this letter the effect of gradually introducing enhanced receivers at mobiles in different locations. With greedy scheduling, capacity, fairness and coverage are quantified and numerically compared according to locations of enhanced mobiles. The results show that the enhancement made at mobiles nearer to the base provides the greater capacity but this capacity-driving introduction of the enhancement makes the fairness and the coverage poorer.

For point-to-point mobile visual communications, layered video has been utilized to adapt to time-varying channel capacity over noisy environments. From the perspective of the HVS (Human Visual System), it is necessary to minimize the loss of visual quality by specifically maintaining the throughput of visually important regions, objects and so on. Utilizing the prioritized bitstreams generated according to each layer, the throughput can be improved for given channel statistics. In this paper, we define the transmission gain and measure the improved performance when the throughput of ROI (Regions Of Interest) is increased relative to visually unimportant regions over a capacity limited mobile channel.

The notion of correlation intractable function ensembles (CIFEs) was introduced in an attempt to capture the "unpredictability" property of random oracles [12]: If O is a random oracle then it is infeasible to find an input x such that the input-output pair (x,O(x)) has some desired property. In this paper, we observe relationships between zero-knowledge protocols and CIFEs. Specifically, we show that, in the non-uniform model, the existence of CIFEs implies that 3-round auxiliary-input zero-knowledge (AIZK) AM interactive proofs exist only for BPP languages. In the uniform model, we show that 3-round AIZK AM interactive proofs with perfect completeness exist only for easy-to-approximate languages. These conditional triviality results extend to constant-round AIZK AM interactive proofs assuming the existence of multi-input CIFEs, where "multi-input" means that the correlation intractability is satisfied with respect to multiple input-output pairs. Also, as a corollary, we show that any construction of uniform multi-input CIFEs from uniform one-way functions proves unconditionally that constant-round AIZK AM interactive proofs with perfect completeness only for easy-to-approximate languages.

To support multimedia applications effectively in mobile networks, the handover latency or packet losses during handover should be very small. Addressing this issue, we present a cooperative mobile router-based handover (CoMoRoHo) scheme for long-vehicular multihomed mobile networks. The basic idea behind CoMoRoHo is to enable different mobile routers to access different subnets during a handover and cooperatively receive packets destined for each other. In general, packet losses are directly proportional to handover latency; however, the overlapped reception of packets from different subnets makes possible to minimize packet losses even without reducing handover latency. To evaluate the scheme, we carried out performance modeling of the CoMoRoHo scheme in comparison with the Fast Handover for Mobile IPv6 (FMIPv6) protocol in regard to the handover latency, packet loss, signaling overhead, and packet delivery overhead in access networks. The analysis results show that CoMoRoHo outperforms FMIPv6 by reducing the packet losses as well as signaling overheads by more than 50%. Moreover, CoMoRoHo imposes lower packet delivery overheads required for preventing packets from being dropped from access routers. We thus conclude that CoMoRoHo is a scalable scheme because its performance remains intact even when the access network is overloaded.

In this paper, we shall describe about a refined theory based on the concept of set-valued operators, suitable for available operation of extremely complicated large-scale network systems. The deduction of theory is accomplished in a weak topology introduced into the Banach space. Fundamental conditions for availability of system behaviors of such network systems are clarified, as a result, in a form of fixed point theorem for system of set-valued operators.

In this paper, a novel location management scheme called Distributed Group Tracking (DGT) for group communications in Cellular IP networks is proposed. In DGT, Base stations track each member of a group and build a share multicast routing tree called DGT-Tree for the group in a distributed manner. Transmission of multicast packets among group members is along the group's DGT-Tree. Simulation study has demonstrated that a better performance can be achieved by DGT over the gateway-based counterpart in terms of transmission cost as well as link load balance. Moreover, the average number of DGT operations decreases as the group size increases, showing the good scalability of the DGT scheme, and the average number of control packets as well as the cache requirement for performing DGT operations demonstrate the moderate overhead introduced by DGT.

Let A(n, d, w) denote the maximum possible number of code words in binary (n,d,w) constant weight codes. For smaller instances of (n, d, w)s, many improvements have occurred over the decades. However, unknown instances still remain for larger (n, d, w)s (for example, those of n > 30 and d > 10). In this paper, we propose a new class of binary constant weight codes that fill in the remaining blank instances of (n, d, w)s. Specifically, we establish several new non-trivial lower bounds such as 336 for A(64, 12, 8), etc. (listed in Table 2). To obtain these results, we have developed a new systematic technique for construction by means of groups acting on some sets. The new technique is performed by considering a triad (G, Ω, f) := ("Group G," "Set Ω," "Action f on Ω") simultaneously. Our results described in Sect. 3 are obtained by using permutations of the elements of a set that include ∞ homogeneously like the other elements, which play a role to improve their randomness. Specifically, in our examples, we adopt the following model such as (PGL2(Fq), P1(Fq), "linear fractional action of subgroups of PGL2(Fq) on P1(Fq)") as a typical construction model. Moreover, as an application, the essential examples in [7] constructed by using an alternating group are again reconstructed with our new technique of a triad model, after which they are all systematically understood in the context of finite subgroups that act fractionally on a projective space over a finite field.

Efficient group rekeying is an important issue for secure group communications. Most of the proposed group rekeying methods require expensive encryption and decryption operations to rekey the group. However, in a model where a trusted server is used to distribute group keys, the trusted server may become a bottleneck because of the expensive computation operations, such as encryption, that it has to perform. In this paper, we propose a new stateless group rekeying scheme to solve the multicast group rekeying problem. In our proposed scheme, the trusted server combines mask-based key-location hiding with the simple XOR-encryption using secret hash values to rekey the group. Without affecting the system security, our approach reduces the processing cost of the trusted server by eliminating the need to encrypt the group key. Moreover, to acquire the group key, the computational cost of the group members is low and stable regardless of the rekeying message size.

This paper studies a multiband mobile communication system to support both high data rate services and wide service coverage, using high and low frequency resources with different propagation characteristics. In the multiband system, multiple frequency bands are managed by a base station and one of the frequency bands is adaptively allocated to a terminal depending on his channel quality. By limiting the low frequency resources to a terminal not covered by the higher frequencies, the presented multiband system can accommodate many terminals providing wide coverage area, as if all radio resources have low frequency. From numerical results, the multiband system can provide wide service coverage area for much larger number of terminals than conventional systems. It is also found that an appropriate balance of multiple frequency resources is essential to achieve high capacity.