Mark C. Cudak

High speed downlink packet access performance

The overall throughout and delay performance of the 1XTREME proposal in 3GPP2 and the HSDPA proposal in 3GPP are provided. The performance sensitivity to call model, peak data rate, hybrid ARQ, C/I feedback delay, and multipath interference is examined using a quasistatic system simulator. In all cases, performance is bounded using two simple scheduling approaches, maximum C/I and round robin.

Streaming Video Capacities of LTE Air-Interface

The 3GPP Long Term Evolution (LTE) systems have been designed to deliver higher peak data rates, higher capacity and lower air-interface latency compared to prior 2G and 3G systems. This high performance will make it possible to support more demanding applications beyond web browsing and voice, which will require higher data rates and QoS guarantees. Video services are becoming very popular over the Internet. With the wide deployment of LTE in the near future, the demand for high data-rate video applications over cellular wireless will grow. However, in order to make these services commercially viable, it is necessary that the LTE air-interface can deliver high quality services to a sizeable number of users simultaneously. In this paper we investigate the downlink video capacities of the LTE air-interface by dynamic system simulation using realistic video traffic models and detailed models of the LTE air-interface. We investigate how video quality and system outage criteria impact the air-interface video capacities and describe observations on video stream quality and operator revenue under certain cost assumptions.

Radio resource control protocol configuration for optimum Web browsing

Web browsing is expected to be one of the most widely used applications over the future generations of wireless networks. The radio resource control (RRC) protocol configuration for maximum radio system capacity and optimum application performance depends on the characteristics of the network, the system and the application data traffic. It is essential to estimate, a priori, the required values of the RRC protocol configuration parameters so that the system can be configured for optimum performance. In this paper we consider the support of Web browsing applications over the 3/sup rd/ generation wireless networks. We perform a sensitivity analysis of the Web browsing performance, system control overhead and the RRC protocol parameter values for various network and application characteristics. We also estimate these RRC parameter values for optimum operating condition considering realistic models of the network, system and applications. From the simulation results, we observe that the required system control overhead for optimum Web browsing performance is small in realistic scenarios of 3/sup rd/ generation wireless networks.

Incremental redundancy for evolutions of 3G CDMA systems

An overview of the hybrid ARQ used by the 3G CDMA evolutions (1xEV-DV for cdma2000 and HSDPA for WCDMA) is provided, along with simulation data supporting several of the key design decisions. Enhancements to AMC and hybrid ARQ operation are also discussed.

Shared channels for packet data transmission in W-CDMA

One of the targets for a wideband CDMA (W-CDMA) system is to provide an efficient transfer of low bit rate to very high bit rate packet data services. A shared channel concept has been proposed for both the downlink and uplink channels that is better suited for bursty packet data traffic. The shared channels allows UEs to transmit and receive data bursts at high rates by using short leases on the radio resource thereby lowering the overall delay by taking the greatest advantage of statistical multiplexing. The high rate bursts require the network tightly manage its resources to insure that the appropriate OVSF codes are assigned on the downlink and the aggregate interference does not exceed the noise rise on the uplink. In both cases, the network must convey the new assignments on a frame by frame basis. In this paper, packet data transmission using both downlink shared channel (DSCH) and uplink shared channel (USCH) is discussed for a W-CDMA system.

Aggressive modulation/coding scheme selection for maximizing system throughput in a multi-carrier system

Multi-carrier modulation techniques, such as OFDM, are attractive propositions for the design of future broadband wireless communication systems due to higher spectral efficiency than CDMA. A capacity enhancing technique to be commonly used in these systems is adaptive modulation/coding (AMC) for link adaptation. With AMC, the modulation and coding scheme (MCS) is selected based on the channel quality information. MCS selection is an imperfect process by nature, due to, for example, the variability of the channel. Moreover, since the set of available MCSs is quantized, it is not always possible to select the optimal rate. Using these non-optimal MCS values results in reduced system capacity. This paper describes a method that attempts to maximize system and user throughputs in a multi-carrier system by overcoming the impacts of such non-optimal MCS selection through the use of hybrid ARQ (HARQ). This method relies on aggressive MCS selection and multiple HARQ transmissions. The performance impact of this method on various types of packet data applications is evaluated by system level simulation. Simulation results indicate that significant system and user throughput gains can be achieved by this method.

Streaming Video Capacity Comparisons of Multi-Antenna LTE Systems

The 3GPP Long Term Evolution (LTE) Release-8 specifications are designed to deliver higher peak data rates, higher throughput and lower air-interface latency compared to 2G and 3G systems. This higher performance will make it possible to support more demanding applications beyond web-browsing and voice, requiring higher data rates and stricter QoS constraints. Video services are becoming increasingly popular over the Internet indicating that the demand for such high data-rate video applications over cellular wireless will continue to grow. However, in order to make these services commercially viable in a LTE system it is necessary for the air-interface to deliver high quality services to a significant number of users simultaneously. In this paper we investigate the video capacity of a LTE air-interface using realistic video traffic models. An LTE air-interface can support multiple-antenna transmit arrays and several multiple antenna transmission modes to increase system capacity. We investigate the benefits of using 4 transmit antennas compared to 2 transmit antennas on the video capacity of an LTE system. The results from our investigation indicate that the capacity benefits with 4 transmit antennas are much higher with video services than those observed with other traffic models such as the full-buffer traffic model. The results also show that a 10MHz TDD LTE system can service upto 48 users per sector with 256Kbps video streams in the downlink indicating that such services can be commercially viable.

Air-interface for 1XTREME/1xEV-DV

A high data rate proposal for a 1.25 MHz DS-CDMA system, called 1XTREME (1xEV-DV), is capable of supporting peak rates of up to 4.8 Mbps and average data rates of approximately 1 Mbps. It is a true evolution of the cdma-2000 CDMA system, being fully backward compatible and therefore able to support both voice and data users on the same carrier. A new forward shared channel (F-SHCH) with an associated forward control channel carries the high-speed packet data. The associated forward control channel structure is shown to offer a 30% increase in the active users on the system over a typical structure. Furthermore, additional channels are added in the reverse link to support the various throughput-enhancing features of 1XTREME. In this paper, the details of the air-interface are presented along with the description of each channel. Also, the simulated performance of the F-SCH and the forward control channels are presented.

Improving the uplink data rate of portable devices in broadband systems with relaying

Wireless broadband systems currently under development, such as IEEE 802.16e and 3GPP-LTE, can use much larger bandwidths than existing 3G systems (up to 20 MHz or more) to provide very high bit rates to a large number of users. When designing a broadband cellular system, it is attractive from a commercial deployment perspective to support reasonably large cell sizes (e.g., 2 km radius), to enable existing cell sites to be reused whenever possible. However, on the uplink, the combination of wide channel bandwidths and practical constraints on the output power of portable, battery operated devices leads to severe limitations on the uplink data rate. Therefore, solutions are needed to ensure good link quality and high data rate capabilities on the uplink without increasing the uplink transmit power. In this paper, the use of fixed single-hop transparent relays on the uplink is shown to significantly improve system performance with a minimal increase in system complexity. Keywords: relay, OFDM, single-hop, EUTRA, 802.16e

Impact of radio resource control mechanisms on the performance of Internet applications

The future generations of wireless networks are being designed to provide various types of packet data services. Radio resource control (RRC) protocols should be designed to configure the radio bearer so that the radio system capacity is maximized, the mobile terminals battery drain is minimized and users traffic requirements are met. It is inevitable that the RRC protocol will affect the performance of the network transport protocols and, in return, the network transport protocols will limit the radio systems ability to schedule resources efficiently. In this paper we describe a genetic model of RRC protocol states, which represents various air interfaces. Using this model, we investigate how the parameters of RRC protocol states affect the radio system control overhead and performance of Web browsing applications.