Abstract: One embodiment of the present invention provides a system that performs a query-based convergecast scheduling in a convergecast network, which includes a base-station and a plurality of nodes. During operation, the system receives a convergecast tree for the convergecast network. Each node in the convergecast tree is associated with a hop-count to the base-station through a specific branch and each node can generate zero or more packets to transmit. Next, the system initializes a query from the base-station, wherein the query is successively propagated to the nodes through the branches. In response to the query, the system computes distributed-timing-information indicating a packet transmission schedule for the nodes. The system next aggregates the distributed-timing-information associated with the nodes toward the base-station through the branches. The system then forwards the aggregated distributed-timing-information to the plurality of nodes.

Abstract: A method that addresses a cross layer optimization technique for TCP in which the need to send ACK frames across wireless links is contained by using the information from the MAC layer acknowledgements is disclosed. More specifically the method significantly reduces bandwidth consumption and improves the performance of TCP on wireless networks. Furthermore, since the number of transmitted and received packets is reduced at the mobile device, the battery life of the device can be improved significantly. The proposed method can also be applied to downlink and uplink ACK frames with a slight variation between the two.

Abstract: What is described is an approach to assigning timeslots of appropriate duration when using a TDMA based MAC protocol for forwarding VOIP traffic. It is known that a typical user speaks only 35% of the time in a voice session. Existing VOIP systems exploit this fact and reduce the amount of data generated by employing Voice Activity Detection (VAD) algorithms. The packets generated when a user is silent are shorter than the packets generated when a user is speaking. Hence there is a need to assign timeslots of different duration based on user speech activity. When the user is speaking we assign an Active Speech Timeslot (AST). When the user is listening a Silent Speech Timeslot (SST) that is long enough to transmit packets generated by a Comfort Noise Generator is assigned.

Abstract: A tri-core architecture for reducing MAC layer processing latency at the base stations is described. The new architecture minimizes the processing delay by introducing a pipelined approach. The fundamental concept involves splitting the Medium Access Control (MAC) layer functionality into three distinct tasks, with each processor performing a given task. All tasks will be thus performed concurrently, avoiding much of the overhead encountered while processing received packets and preparing packets to be transmitted.

Abstract: A system and method for a mobile switching center to efficiently manage; assign; and reclaim the IP addresses is described. The procedure utilizes a mechanism that involves splitting the IP address assignment functionality into two parts, with the Base Station being responsible for assigning IP addresses to individual end user devices and the mobile switching center assigning a block of IP addresses to each Base Station and includes a methodology for the mobile switching center to efficiently manage; assign and reclaim the IP addresses.

Abstract: A scanning technique to select the best channel a mobile handset needs when approaching handoff is described. More specifically a system and method for an adaptive proactive scanning mechanism in which the rate of scanning is determined by the necessity to handoff and battery power is disclosed.

Abstract: A technique for network entry in multi-channel mobile systems is described. The procedure utilizes the channel specific information sent in the beacon of each channel to select a subset of suitable channels. It then proceeds to scan these channels to gather information on perceived interference and received signal strength. Based on collected information the device picks the most suitable channel for joining the network. Since the channels to be scanned are pre-selected based on information seen in the beacon, the overall scan latency is reduced, thereby leading to a faster and more successful network entry.

Abstract: In this disclosure a technique of base station assisted mobility detection of handsets is described. More specifically by transmitting the subnet ID in the Beacon, a base station simplifies the process of network detection. This also leads to a significant reduction in handoff latency by giving the handset ample time to prepare for the impending handoff.

Abstract: In wireless networks where the goal is to support a large number of VOIP based cellular calls, large overhead headers in RTP voice packets are not acceptable. In wireless networks where multiple base stations are deployed, handsets may handoff from one base station to the other while in a voice call creating a large overhead. This disclosure describes an efficient way to extend a header compression algorithm and lower the overhead when the handset is in a voice call and hands off from one base station to another.

Abstract: A heterogeneous back-off algorithm wherein latency-intolerant messages follow a linear back-off and other messages follow an exponential back-off protocol is disclosed. Typically exponential back-off techniques are used to schedule retransmissions to increase the probability of successful transmission in temporally high contention scenarios. However, exponential back-off can create an exponential increase in the transmit latency. For transmitting latency-intolerant messages like handoff messages large latency is not acceptable therefore a heterogeneous back-off algorithm using both back-off protocols is proposed.

Abstract: A mechanism is disclosed where a Base Station provides assistance to a mobile device in the channel-switch process because a mobile device might have to perform frequent channel switches to overcome adverse channel conditions due to interference in the 900 MHz ISM band. The Base Station broadcasts channel-specific information that will be used by all mobile devices to accurately select prospective channels for future channel-switches, thereby cutting down the latency that is experienced during an actual switch.

Abstract: A mechanism for decreasing the latency in an IP address assignment process for mobile systems using IP as network layer protocol is described. The proposed system is aimed at supporting seamless hand-offs for real-time applications like VOIP. A set of optimized messages is defined to eliminate the need for exchanging long DHCP messages to acquire an IP address. The mechanism involves splitting the IP address assignment functionality into two parts, with the base station being responsible for assigning IP addresses to individual end user devices, and the Mobile Switching Center assigning a block of IP addresses to each base station.

Abstract: An extension to a heterogeneous MAC protocol that makes provisions for multi-frequency system architecture is described. A new frame structure for a multi-frequency xMAX system is introduced. Multi-frequency xMAX system is an extension of a single-channel xMAX system, where the available bandwidth is split into multiple channels to provide additional capacity and range. The new frame structure is followed by all channels and is designed to fulfill the requirements of multiple frequency operation. The new frame structure incorporates features that allow the handset to leverage the advantages of multiple frequency channels, especially in the event of interference. Also, a new mechanism to reduce the power consumption in the handset is discussed that significantly reduces the number of unnecessary receive operations at the handset.

Abstract: A tri-core architecture for reducing MAC layer processing latency at the base stations is described. The new architecture minimizes the processing delay by introducing a pipelined approach. The fundamental concept involves splitting the Medium Access Control (MAC) layer functionality into three distinct tasks, with each processor performing a given task. All tasks will be thus performed concurrently, avoiding much of the overhead encountered while processing received packets and preparing packets to be transmitted.

Abstract: This disclosure describes a new keep alive timeslots based method to track registered handsets for a MAC protocol that combines contention-free and contention-based MAC protocols into a heterogeneous MAC protocol used for forwarding VoIP traffic in VoIP systems on wireless networks using multiple base stations thus allowing for transmission of high bit-rate data to multiple users over wired and wireless means.

Abstract: This disclosure describes a provisional hand-off mechanism to transfer handsets between base stations for a MAC protocol that combines contention-free and contention-based MAC protocols for use in wireless VoIP systems with multiple base stations that reduces packet overhead thus allowing for transmission of high bit-rate data to multiple users over wired and wireless means.

Abstract: This disclosure describes a new a header compression method for a MAC protocol that combines contention-free and contention-based MAC protocols into a heterogeneous MAC protocol used for forwarding VoIP traffic in VoIP systems on wireless networks using multiple base stations that reduces packet overhead thus allowing for transmission of high bit-rate data to multiple users over wired and wireless means.

Abstract: This disclosure describes a new interference avoidance Medium Access Control (MAC) protocol that combines contention-free and contention-based MAC protocols into a heterogeneous MAC protocol used for forwarding VoIP traffic in VoIP systems on wireless networks using multiple base stations which addresses additional interference elimination and the need to transport high bit-rate data to multiple users over wired and wireless means.

Abstract: This disclosure describes a new Medium Access Control (MAC) protocol that combines contention-free and contention-based MAC protocols into a heterogeneous MAC protocol used for forwarding VoIP traffic in VoIP systems on wireless networks using multiple base stations which addresses the need to transport high bit-rate data to multiple users over wired and wireless means.

Abstract: What is described is an approach to assigning timeslots of appropriate duration when using a TDMA based MAC protocol for forwarding VOIP traffic. It is known that a typical user speaks only 35% of the time in a voice session. Existing VOIP systems exploit this fact and reduce the amount of data generated by employing Voice Activity Detection (VAD) algorithms. The packets generated when a user is silent are shorter than the packets generated when a user is speaking. Hence there is a need to assign timeslots of different duration based on user speech activity. When the user is speaking we assign an Active Speech Timeslot (AST). When the user is listening a Silent Speech Timeslot (SST) that is long enough to transmit packets generated by a Comfort Noise Generator is assigned.