Context-based binary arithmetic coding (CBAC) is an entropy coder of AVS 2.0, the latest Chinese video compression standard for 8K ultra-high-definition (UHD) video, which employs a logarithmic number system to avoid multiplication operations for range updates for binary arithmetic coding (BAE). In this paper, we propose a high-throughput CBAC hardware encoder for 8K UHD. To enhance its throughput, we introduce a bin-merging technique that converts a subsequence of bins into a merged bin without affecting the functionality of the CBAC encoder. Moreover, we also employ a 4-stage pipeline architecture for CBAC and lookup tables for context updates. Consequently, the proposed CBAC encoder can process about 3.94 bins per cycle and achieve a throughput of 2.9 Gbins per second. When synthesized in a TSMC 65nm LP process, it operates up to 735 MHz and the total gate count is 182.5 K. To the best of our knowledge, this is the highest throughput for a CBAC encoder.

In this paper we compare the coding efficiency of AVS 2.0[1] for engines of the Context-based Binary Arithmetic Coding (CBAC)[2] in the AVS 2.0 and the Context-Adaptive Binary Arithmetic Coder (CABAC)[3] in the HEVC[4]. For fair comparison, the CABAC is embedded in the reference code RD10.1 because the CBAC is in the HEVC in our previous work[5]. The rate estimation table is employed only for RDOQ in the RD code. To reduce the computation complexity of the video encoder, therefore we modified the RD code so that the rate estimation table is employed for all RDO decision. Furthermore, we also simplify the complexity of rate estimation table by reducing the bit depth of its fractional part to 2 from 8. The simulation result shows that the CABAC has the BD-rate loss of about 0.7% compared to the CBAC. It seems that the CBAC is a little more efficient than that the CABAC in the AVS 2.0.

A compound instruction, encoding several ALU or memory operations within an instruction word, has been regarded as an efficient way of improving performance. In the compiler for embedded processors, the code generation algorithm for compound instructions has been built by dealing mainly with instruction selection which is a crucial phase of code generation. In this paper, we propose an iterative code generation algorithm for minimizing the detrimental impact of register coalescing that is applied to the code with compound instructions generated earlier from the instruction selection phase.

Femto BS (base station) is emerging as a key technology to secure the coverage and capacity in indoor environments. However, since the existing macrocell network is overlaid on femtocell networks utilizing the same set of frequency channels, femtocell networks can originate severe co-channel interference to the macrocell network unless the femtocell network is carefully configured. Therefore, according to a desired network-wide objective, we optimize the femtocell network with constraints such that the service connectivity with a femto BS is secured in the target indoor area while the signal emitted out of the building, playing as interference to the outdoor users, should be controlled with an appropriate strength in order not to interrupt the communication between macro BS and outdoor users. Each optimization problem is formulated as a mixed integer programming, and as the results, we obtain not only the transmit power and operational frequency channel of each femto BS, but also the optimal femto BS-to-user association pair at each geographical position.

The ideal design for VoIP should be able to maximize the number of concurrent users while each admitted user enjoys the satisfactory quality of voice communication. In a recent packet-based wireless system, the quality-of-service (QoS) provisioning for VoIP raises several challenging issues including correlated delay performance among users and the rate-reliability tradeoff in managing multiple transmission rates on top of the inherent difficulty originating from the dependency of QoS on end-to-end delay. For these reasons, it is rarely found in the literature the work which presents the admission criteria for VoIP in an explicit manner. In this paper, our major contributions include 1) deriving the link-level QoS requirement from the E-model; 2) presenting the admission criteria in an explicit manner; 3) proposing a transmission rate adaptation algorithm specialized for VoIP application; and 4) illustrating the feasibility of our proposed schemes by getting the necessary information from the measurement. In addition to the theoretical justification, through the intensive simulation study in the Rayleigh fading environment, we prove that our joint designs composed of the rate adaptation, measurement-based admission control algorithm, and its extension to supporting the cell-boundary users indeed work well. Also, we evaluate the impact of various parameters including the average SNR, the Doppler rate, and the wireline delay.

This paper considers two issues arising in an integrated IEEE 802.16e/802.11 network: (1) finding a possible network, which mobile station (MSTA) can switch to, and (2) making a decision whether to execute a vertical handoff (VHO). For this purpose, we propose that 802.16e Base Stations (BSs) periodically broadcast the information about the density of 802.11 access points (APs) within their cell coverage. Based on this information, we develop a novel model, which predicts the successful scan probability during a given scan time. Using this analytical model, we devise an energy-efficient scan policy (ESP) algorithm, which enables an MSTA to decide (1) whether to attempt to discover APs in the current 802.16e cell, and (2) if so, how to set the 802.11 active scan interval considering the energy consumption. For the VHO decision, we mainly consider the impact of the service charge. Especially, a practical service fee models, i.e., flat pricing for WLAN and partially-flat pricing for 802.16e network, are considered. Under this service charge plan, we need to control the usage of the 802.16e network to minimize the user's payment. To this end, we propose a scheme, which intelligently postpones the delivery of the delay-tolerant traffic within a certain time limit combined with ESP algorithm.

In the wireless data systems, automatic repeatrequest (ARQ) is used in order to reliably deliver packets to the upper layer while hybrid ARQ (HARQ) intends to improve the reliability over the air through the combination with other transmission techniques, e.g., modulation and channel coding. While the two functions are complementary to each other, it has been typically recognized as if they work independently at their corresponding layer. However, we note that the retransmission via ARQ is correlated with whether HARQ eventually delivers a packet successfully within a retransmission limit. Capturing this observation, we in this paper introduce a new ARQ feedback scheme called Cross-Layer ARQ (CL-ARQ). CL-ARQ makes use of the acknowledgement of HARQ internally. CL-ARQ not only allows ARQ to operate without explicit acknowledgement, but also improves the reliability combined with existing ARQ protocols. Especially, when the entities in charge of HARQ and ARQ are located far apart geographically, we show that CL-ARQ remarkably outperforms other schemes. Additionally, CL-ARQ is shown to resolve the stall problem, which occurs when the link capacity can not be fully utilized due to the limitation of ARQ window size. We evaluate the performance of CL-ARQ via both analysis and simulations.

To provide heterogeneous quality-of-service (QoS) to various applications, the bandwidth of orthogonal frequency division multiplexing (OFDM) is divided into multiple number of sub-bands, which employ a different set of transmission technologies, such as multiple-input multiple-output (MIMO), packet scheduling, adaptive modulation and coding (AMC), and hybrid automatic repeat request (HARQ) depending on the traffic type. According to this concept, DiffSeg system, where the two-dimensional resource domain of OFDM is filled with four different resource units, called segments, and the occupancy ratio of each type of segment is determined by the segment map, has been recently proposed in [5][6]. In this paper, we introduce a concept of segment diversion to utilize the radio resource more efficiently considering the status of QoS. We then propose a system optimization model, which finds an optimal segment map and diversion ratios of real-time (RT) connections in order to maximize the residual resource for non-real-time (NRT) traffic while satisfying the minimum QoS requirement of RT traffic. We formulate an optimization problem using mixed integer programming, and then develop two computationally efficient algorithms: simplex-based heuristic and Maximum Diversion Rule. Especially, Maximum Diversion Rule is shown to achieve a near-optimal solution with dramatically less complexity.

In this paper, we evaluate and enhance the performance of a Forward Error Correction (FEC) scheme for IEEE 802.11 Medium Access Control (MAC). A novel retransmission combining technique is proposed to enhance the performance of the MAC-level FEC scheme.,We also identify the problem with the IEEE 802.11a physical (PHY) layer when it is used with the MAC-level FEC. A new PHY frame format, backward compatible with the original format, is proposed to resolve the problem. Finally, we analytically evaluate the error performance of the MAC-level FEC, and its enhanced performance via retransmission combining and new 802.11a PHY frame format in AWGN environment. Additionally, we present and discuss the results from simulations using TCP/UDP traffic in more realistic channel environments.

Automatic repeat request (ARQ) is one of the effective techniques against the transmission error at the medium access control (MAC) layer. An erroneous MAC protocol data unit (MPDU) can be typically retransmitted within a given limit. In order to improve the IP-level performance, which directly affects the user-perceived quality-of-service (QoS), we propose a different ARQ strategy, called 'MSDU-based' scheme, with simple and minor modification from the existing ARQ concept. We evaluate the analytical IP-level performance of both the conventional and proposed scheme.