Abstract: To improve throughput rates of packets transmitting positive train control (PTC) messages in an asynchronous wireless network that supports controlling movement of trains, data rates are adjusted based one or more conditions of the link. Modulation and coding schemes with less overhead can be employed to increase the data rate at which information is transferred when an estimated link quality or conditions are relatively good. Conversely, when the estimated link quality is relatively poor, more robust modulation and coding schemes for transmissions can be used to maintain link performance but at the cost of reduced data rates. Optionally, if the estimated link quality is higher than required to achieve a predefined maximum transmit rate at a given default power rate, transmit power can be reduced to that necessary for transmit at the predefined maximum transmit rate.

Abstract: A method of exchanging application messages generated by an applications with a format specified by a predetermined protocol and then encapsulating the message with a railroad edge messaging protocol (EMP) header and a railroad Class D messaging transport header to form a packet for transmission across a railroad communications system.

Abstract: A method of exchanging application messages generated by an applications with a format specified by a predetermined protocol and then encapsulating the message with a railroad edge messaging protocol (EMP) header and a railroad Class D messaging transport header to form a packet for transmission across a railroad communications system.

Abstract: A method of exchanging centralized train control (CTC) messages in a railroad communication system includes generating a message having a format defined by a protocol with an application running on a sending one of a railroad wayside system and a railroad dispatch system. A railroad edge messaging protocol (EMP) header and a railroad Class D messaging transport header are appended to the message to generate a packet. The packet is transmitted to a receiving one of the railroad dispatch system and the railroad wayside system across the railroad communications system.

Abstract: A method of messaging in a communications system includes generating a message at an application layer. The message and associated message handling codes are passed to a transport layer and the message fragmented. The fragmented message and the message handling codes are passed to a network layer and the fragmented message selectively segmented as indicated by the message handling code. The selectively segmented message and the message handling code are passed to a link layer and formed into a packet including packet type information and data parts. The packet is passed to a physical layer and a preamble is added. The preamble and packet are transmitted with a radio.

Abstract: A radio receiver including a memory storing a reference sample sequence and a synchronizer. The synchronizer receives a data packet, samples and modulates symbols from the data packet and then generates phase-information samples from the modulated samples. The phase-information samples are low-pass to generate a filtered phase-information sample sequence. Samples of the filtered phase-information sample sequence are selectively compared with samples of the reference sample sequence and bit synchronization is established when a selected number of samples of the filtered phase-information sample sequence match a selected number of samples of the reference sample sequence.

Abstract: A method for implementing communications in a railroad communications system having a base station radio and remote radios, the remote radios including a mobile radio and a wayside radio. The method includes assigning a common radio communications channel for allowing a remote radio to connect with the base station radio using a carrier sense multiple access (CSMA) communications protocol and assigning a local channel for allowing communications between the radio base station and the remote radios and between the remote radios, wherein communications on the local channel utilizes a selected one of fixed time division multiple access (FTDMA) and dynamic time division multiple access (DTDMA) communications protocols.

Abstract: A method for implementing communications in a railroad communications system having a base station radio and remote radios, the remote radios including a mobile radio and a wayside radio. The method includes assigning a common radio communications channel for allowing a remote radio to connect with the base station radio using a carrier sense multiple access (CSMA) communications protocol and assigning a local channel for allowing communications between the radio base station and the remote radios and between the remote radios, wherein communications on the local channel utilizes a selected one of fixed time division multiple access (FTDMA) and dynamic time division multiple access (DTDMA) communications protocols.

Abstract: A power controlled sub-band assignment and power allocation among users in a multiband UWB system aims to reduce power consumption without compromising performance. The overall transmit power is minimized under the practical constraints, including packet error rate, transmission rate, and FCC regulations. To insure the system feasibility in variable channel conditions, an optimization scheme manages the assignment of UWB devices to respective channels subject to their suitability to the requested users' transmission rates. An inexpensive suboptimal approach reduces the complexity of the optimization procedure and achieves a comparable performance to those of the complex full search optimization routine. The suboptimal scheme obtains the feasible solutions adaptively when the channels assignment, initially calculated under the optimization criteria, is not feasible for the user's rate requirement.

Abstract: A power controlled sub-band assignment and power allocation among users in a multiband UWB system aims to reduce power consumption without compromising performance. The overall transmit power is minimized under the practical constraints, including packet error rate, transmission rate, and FCC regulations. To insure the system feasibility in variable channel conditions, an optimization scheme manages the assignment of UWB devices to respective channels subject to their suitability to the requested users' transmission rates. An inexpensive suboptimal approach reduces the complexity of the optimization procedure and achieves a comparable performance to those of the complex full search optimization routine. The suboptimal scheme obtains the feasible solutions adaptively when the channels assignment, initially calculated under the optimization criteria, is not feasible for the user's rate requirement.