The effect of spatial diversity on the throughput and reliability of wireless networks is examined. Spatial diversity is realized through multiple independently fading transmit/receive antenna paths in single-user communication and through independently fading links in multiuser communication. Adopting spatial diversity as a central theme, we start by studying its information-theoretic foundations, then we illustrate its benefits across the physical (signal transmission/coding and receiver signal processing) and networking (resource allocation, routing, and applications) layers. Throughout the paper, we discuss engineering intuition and tradeoffs, emphasizing the strong interactions between the various network functionalities.

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Great expectations: the value of spatial diversity in wireless networks

A method of adaptively scheduling communications in a wireless mesh network including a plurality of network nodes includes generating a network routing scheme based on a topology of the wireless mesh network, generating a communication schedule for the wireless mesh network, and automatically updating the communication schedule in response to detecting a change in a transmission requirement of at least one of the plurality of network nodes. The act of generating a communication schedule includes defining a communication timeslot of a predefined duration and defining a plurality of superframes as repeating cycles of a certain number of consecutively scheduled communication timeslots.

Adaptive scheduling in a wireless network

Mobile terminal communicating resource requests for dedicated uplink channel resources in a mobile communication system and method for communicating resource requests for dedicated uplink channel resources in a mobile communication system. To allow the serving cell to detect "DOWN" commands from non-serving cells during soft handover the invention suggests a new definition of criteria for setting the "happy bit" in the control information associated to data transmitted on dedicated uplink channels. According to these criteria the mobile terminal may not indicate an unhappy condition while ramping up resource utilization. Only if resources equivalent to the maximum serving grant are utilized, the transmission buffer status requires to and the power status of the terminal allows for the happy bit is set to indicate a unhappy condition.

"happy bit" setting in a mobile communication system

A method of routing a data packet between a first node and a second node on a communication network includes defining a first graph through the first node and the second node and zero or more intermediate nodes, associating several nodes which belong to the communication network with the first graph, associating a first unique graph identifier with the first graph and providing at least partial definitions of the first graph and the first unique identifier to at least some of the nodes associated with the first graph. The method then sends data packet with the graph identifier from the first node, and directs the data packet to the second node via the zero or more intermediate nodes using the graph identifier. This method may include forwarding the packet to a neighbor node of an intermediate node if the intermediate node and the neighbor node are nodes associated with the first graph and if the intermediate node and the neighbor node are connected by at least one direct communication connection.

Routing packets on a network using directed graphs

A method of efficiently operating a wireless communication network in a process control environment, such that the wireless communication network includes a plurality of field devices, includes defining a communication protocol for supporting wireless communications between pairs of the plurality of field devices, including providing a set of protocol commands, transferring process control data from at least some of the plurality of field devices using a first subset of the set of protocol commands of the communication protocol, and transferring network management data to at least some of the plurality of field devices using a second subset of the set of protocol commands of the communication protocol.

Support for network management and device communications in a wireless network

WCDMA release 5 supports peak bitrates for data services in the order of 10 Mbit/s, together with reduced delays and increased system throughput. In this paper, a brief introduction to release 5 is given and radio resource management principles associated with the high speed packet data bearers are discussed. Scheduling performance for WWW services, provision of bearers for streaming services, as well as the simultaneous use of high speed packet data bearers and conversational bearers is elaborated upon. Simulation results indicate that with appropriate radio resource management, all the above challenges may be successfully dealt with.

Performance of WCDMA high speed packet data

In the current WCDMA standard, support for transmit diversity is provided in the down-link to combat fading and changing interference situations. The base station (node B) is equipped with two transmit antennas, while the terminal (user equipment, UE) uses only a single antenna. This arrangement is advantageous compared to receive diversity as it removes the need for two antennas in the terminal. This paper describes the various transmit diversity schemes in WCDMA and gives simulation results, both at the link and system levels. It is found that transmit diversity can greatly improve the system capacity.

Transmit diversity in WCDMA: link and system level results

A load control method is described herein that enables a base station to broadcast three downlink signals including a busy indicator, a maximum resource indicator and a minimum resource indicator to a mobile terminal. In response to receiving the downlink signals, the mobile terminal limits the utilization of a resource (e.g., bit rate, transmission power, power offset) it uses to transmit data to the base station. The mobile terminal may also send an uplink signal including a resource request to the base station. The base station can use the resource request to change the downlink signals if needed. It is with the proper use of these uplink/downlink signals that the behavior of the base station can be automatically optimized to the load situation.

Load control in shared medium many-to-one communication systems

We present the potential performance improvements attainable by new enhancements to the WCDMA uplink. Improvements can be expected in both system capacity and end-user perceived performance. In this paper we focus on the capacity gains of short TTI, hybrid ARQ and scheduling in node-B. The performance is studied from both the link-level and system-level perspectives. The link performance results focus on the gains obtained by the introduction of short TTI and hybrid ARQ with soft combining in node-B. In the system performance results, we also evaluate node-B based rate scheduling for both 2 ms TTI and 10 ms TTL. Our studies indicate that with the introduction of enhanced uplink the gain in uplink capacity can be in the order of 70-100%.

System performance of WCDMA enhanced uplink

To support high peak rates the possibility to use higher-order modulation is included in the WCDMA high-speed downlink shared channel (HS-DSCH). In an initial roll-out, higher-order modulation may not be available in all terminals and it is therefore interesting to understand to what extent enhancements offered by HS-OSCH depends on higher-order modulation. We study the impacts of higher-order modulation on HS-DSCH system performance. Our results indicate that performance gains when introducing HS-DSCH are significant, even if higher-order modulation is not available. When time dispersion is small, higher-order modulation may improve system throughput. To take advantage of higher-order modulation in environments with significant time dispersion advanced receivers structures should be considered. Furthermore, higher order modulation is found to be more sensitive to errors in the channel quality estimates.

M. Samuelsson

Papers

Performance of WCDMA high speed packet data

Transmit diversity in WCDMA: link and system level results

Load control in shared medium many-to-one communication systems

System performance of WCDMA enhanced uplink

Impacts of higher order modulation on HS-DSCH system performance