US 5,822,313 AGranted

Seamless handover in a cordless TDMA system

AssigneeNational Semiconductor Corporation

InventorsCharles J. Malek, David L. Weigand, Dennis M. Rose, Gerard G. Socci

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Abstract

A technique is disclosed for allowing a seamless handover between base stations in a TDMA controller as a telephone handset is transported from one base station's area to another. The disclosed circuitry enables the TDMA controller to assess the quality of the handover before switching to the new base station. When it is determined that a handover operation is to commence, transmissions are made in the original slot time and a handover slot time within the same frame. Also during the same frame, data is received at two separate slot times. Only when it is determined that the data received in the handover slot time contains no transmission errors is the handover completed by then only transmitting on the handover slot transmit time and receiving on the handover slot receive time. In the preferred embodiment, it is determined whether the received data contains no transmission errors by detecting the CRC codes, the signal strength, and the existence of any invalid words.

Claims16

Dependent claims

A device for use in a TDMA communication system, said system including a plurality of base stations for transmitting bursts of data within time slots to handsets and receiving bursts of data within time slots from said handsets, said slots being arranged in frames, said device comprising:

a means for determining whether a handover operation is to be commenced for transferring communication support for a cordless handset from an original base station to a handover base station in a TDMA system;
a transmit buffer for storing data to be transmitted;
a first receive buffer for receiving data from a first burst;
a second receive buffer for receiving data from a second burst;
a switch connected to said first receive buffer and said second receive buffer;
a decoder connected to said switch for receiving data within said first receive buffer or said second receive buffer, depending on a position of said switch;
a first addressing means for addressing locations in said transmit buffer for transmitting said data in said transmit buffer in an original slot transmit time and in a handover slot transmit time within a single frame;
a second addressing means for addressing locations in said first receive buffer at particular times for storing data received in an original slot receive time and for addressing the same locations at said particular times in said second receive buffer for storing data received in a handover slot receive time;
and
a control circuit for detecting whether a handover operation should be completed and, upon detecting that said handover operation should be completed, controlling said switch to route data in said second receive buffer to said decoder for further processing.

7 more elements

A method for performing a seamless handover from an original base station to a handover base station in a TDMA communication system, said system including a plurality of base stations for transmitting bursts of data within time slots to handsets and receiving bursts of data within time slots from said handsets, said slots being arranged in frames, said method comprising the steps of:

transmitting data to said original base station in an original slot transmit time and receiving data from said original base station in an original slot receive time;
determining that a handover operation from said original base station to said handover base station is to commence;
transmitting data in said original slot transmit time and a handover slot transmit time within a single frame;
receiving data in said original slot receive time and a handover slot receive time within said single frame;
storing data from said original slot receive time in address locations in a first storage buffer at particular times and storing data from said handover slot receive time at the same address locations in a second storage buffer at said particular times;
decoding received data within said original slot receive time and converting said received data into decoded signals;
determining that data received in said handover slot receive time meets predetermined criteria for said data to be error-free;
decoding received data within said handover slot receive time from said second storage buffer and converting said received data into decoded signals;
and
ceasing transmission of data in said original slot transmit time and ceasing reception of data in said original slot receive time.

7 more elements

Dependencies are inferred from the claim text.