This paper discusses several practical issues related to the provision of video-on-demand (VOD) services, focusing on retrieval of video data from disk on the server. First, with regard to system design, the pros and cons of cycle-based scheduling algorithms for VOD servers are compared, and an adequate policy according to system configuration is presented. Second, we present a way to tune the cycle-based scheduling algorithm so that it maximizes profit. Third, a method to overcome the cons of cycle-based scheduling algorithms is proposed, and its cost is analyzed.

In this letter, we propose a low-complexity estimation method of cyclic-prefix (CP) length for a discrete multitone (DMT) very high-speed digital subscriber line (VDSL) system. Using the sign bits of the received DMT VDSL signals, the proposed method provides a good estimate of CP length, which is suitable for various channel characteristics. This simple estimation method is consistent with the initialization procedure of T1E1.4 multi-carrier modulation (MCM)-based VDSL Standard. Finally, simulation results with VDSL test loops are presented.

This paper discusses real-time language recognition by 1-dimensional one-way cellular automata (OCAs) and two-way cellular automata (CAs), focusing on limitations of the parallel computation power. To clarify the limitations, we investigate real-time recognition of cyclic strings of the form uk with u {0,1}+ and k 2. We show a version of pumping lemma for recognizing cyclic strings by OCAs, which can be used for proving that several languages are not recognizable by OCAs in real time. The paper also discusses the real-time language recognition of CAs by prefix and postfix computation, in which every prefix or postfix of an input string is also accepted, if the prefix or postfix is in the language. It is shown that there are languages L Σ+ such that L is not recognizable by OCA in real-time and the reversal of L and the concatenation LΣ* are recognizable by CA in real-time.

In a quasi-synchronous reverse link multicarrier code division multiple access system, the signal detection is vulnerable to the interference due to the insufficient guard interval. A multiuser detection with intersymbol interference cancellation is a potential solution to overcome this problem. In this paper, we proposes a parameter acquisition technique based on a specially designed training sequence for the receiver. The concerned parameters are the transformed signature sequences and the ISI generation sequences. We analyze a criterion for the training sequences to achieve the minimum mean square error and propose the systematic generation of the optimum training sequences. We also propose the noise variance estimator for providing information about noise variance to some classes of multiuser detection. Simulation results prove relevant benefits of the proposed techniques and give useful insights into the system designs.

This paper presents a mobility management scheme that combines host-based routing (HBR) with prefix routing to achieve balanced loading of network nodes in a distributed hierarchically arranged mobile IPv6 access network. This allows the higher-level nodes to be less loaded than in pure host based routing schemes, where the root node presents a capacity bottleneck to the system. As a result, this scheme achieves good savings in memory by reducing host-specific caches, and thus enhances network scalability. A direct consequence of reduced database entry is reduced processing latencies at the nodes, which reduces delay and improves on network performance. Our hybrid HBR scheme performs better than the pure HBR schemes in memory conservation and increased network capacity.

Many algorithms have been introduced to obtain giga-bit routing performance by reducing searching time. As most of them, however, have not considered the importance of update time and memory requirement seriously, they couldn't work well in real networks. We propose a flexible and fast IP lookup algorithm, named FFILA, considering these factors and compare the performance of our scheme with that of the conventional scheme of Patricia trie.

This paper investigates prefix computations on Iterative Arrays (IAs) with sequential input/output mode. We show that, for any language L accepted by a linear-time IA, there is an IA which, given an infinite string a1a2 ai, generates the values of χL(a1),χL(a1a2),,χL(a1a2 ai), at steps 4,16,,4i2,, respectively. Here, χL:Σ*{0,1} is the characteristic function of the language L Σ*, defined as χL(w) = 1 iff w L. We also construct 2i3-time and i4-time prefix algorithms for languages accepted by quadratic-time and cubic-time IAs, respectively.

In this note, we present some results about parses of codes. First we present a sufficient condition of a bifix code to have the bounded indicator. Next we consider a proper parse, introduced notion. We prove that for a strongly infix code, the number of proper parses is at most three under some condition. We also prove that if a code X has a unique proper parse for each word under the same condition, then X is a strongly infix code.

A novel scheme of subband adaptive array for multicode Direct Sequence Code Division Multiple Access (DS-CDMA) is proposed in this paper. The proposed scheme has a flexible configuration which allows basestation to be able to dynamically adapt to multirate transmission requests from subscribers. It is shown that the novel scheme can effectively suppress multiple access interferences (MAI) by appropriately forming main beam toward the desired user while pointing beampattern nulls toward MAI sources. Moreover, the combination of the subband adaptive array with the so-called cyclic prefix spreading code CDMA is also proposed to mitigate multipath fading and maximize diversity gain in multipath fading environment.

In the Internet, the routing system consists of the Interior-domain and the Inter-domain. Within the Inter-domain routing, Autonomous System (AS) represents the administrative network domain, which is managed by a single institution with its operational policy. ASs exchange the ASs' reachability information to each other. Without the Inter-domain routing scheme, the nodes in the Internet can't communicate across the multiple ASs. The Inter-domain routing is an essential functional element in the global Internet operation. However, due to several reasons such as miss-configuration at the routers, the Inter-domain routing becomes unstable. This occurs that one AS (say AS1) propagates the prefix that has been already assigned to another AS (say AS2) and other peers receive its routing update and inject the misconfigured AS information to their peering routers. Since the routing information associated with AS1 is over written by AS2, AS1 loses the network connectivity. This problem is known as the Conflict Origin AS prefix or the Multiple Origin AS. We recognize that this is a serious problem which degrades the quality of Internet backbone infrastructure. We focus on this problem and propose the mechanism that can detect the Conflict Origin AS prefix automatically using the policy database. Based on the evaluation using the prototype system, we demonstrate that the proposed mechanism can work well with the existing Internet's Inter-domain routing system.

This paper presents the theoretical analysis of subband adaptive array combining cyclic prefix transmission scheme (SBAA-CP) in multipath fading environment. The exact expressions for optimal weights, array outputs and the output signal to interference plus noise ratio (SINR) are derived. The analysis shows that use of the cyclic prefix data transmission scheme can significantly improve the performance of subband adaptive array (SBAA). An example of implementing SBAA-CP as a software antenna is also presented.

We consider the following three statements for a code L. (P1) For every n 2, both wn Ln and wn+1 Ln+1 imply w L. (P2) For every n 2, if wn Ln, then w L. (P3) For every m, k 2 with m k, wk Lm implies w L. First we show that for every code L, P1 holds. Next we show that for every infix code L, P2 holds, and that a code L is an infix code iff P2 holds and L is a weakly infix code. Last we show that for every strongly infix code L, P3 holds, and that a code L is a strongly infix code iff P3 holds and L is a hyper infix code.

The VLSI implication of the guard interval in orthogonal frequency-division multiplexing (OFDM) systems is described. A new OFDM transmission scheme using cyclic suffix is proposed to reduce the hardware complexity required for implementing the guard interval in the transmitter, and is shown to have the same performance as the conventional approach using cyclic prefix, even with a significantly lower hardware complexity (smaller buffer size and no processing delay).

We consider syntactic congruences of some codes. As a main result, for an infix code L, it is proved that the following (i) and (ii) are equivalent and that (iii) implies (i), where PL is the syntactic congruence of L. (i) L is a PL2-class. (ii) Lm is a PLk-class, for given two integers m and k with 1 m k. (iii)L* is a PL*-class. Next we show that every (i), (ii) and (iii) holds for a strongly infix code L. Moreover we consider properties of syntactic conguences of a residue W(L) for a strongly outfix code L.

This letter proposes an initial frame synchronization algorithm for orthogonal frequency division multiplexing (OFDM) systems. Since the proposed scheme utilizes only the cyclic prefix and the phase shift of the demodulated data without the aid of any known signals, it can be applied not only at the beginning of data transmission but also at any instant during transmission. The performance of the proposed algorithm is confirmed by computer simulation for QPSK, 8-PSK, and 16-QAM systems.

We study some sufficient conditions of codeword lengths for the existence of a fix-free code. Ahlswede et al. proposed the 3/4 conjecture that Σi=1n a-li 3/4 implies the existence of a fix-free code with lengths li when a=2 i. e. the alphabet is binary. We propose a more general conjecture, and prove that the upper bound of our conjecture is not greater than 3/4 for any finite alphabet. Moreover, we show that for any a2 our conjecture is true if codeword lengths l1,l2,. . . consist of only two kinds of lengths.

We introduce a strongly infix code. A code X is a strongly infix code if X is an infix code and any catenation of two words in X has no proper factor in X, which is neither a left factor nor a right factor. We show that the class of strongly infix codes is closed under composition, and, as the dual result, that the property to be strongly infix is inherited by a component of a decomposition.