Single Slot DTM for GSM Speech Quality and Capacity
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Solution Overview
Problem
Current single-slot dual transfer mode (DTM) in GSM/GPRS/GERAN networks can only operate with half-rate speech, leading to speech quality degradation and limited capacity in congested cells, as it cannot utilize full-rate speech channels while maintaining simultaneous voice and data transfer.
Innovation Solution
A new single-slot DTM operation that allows simultaneous speech and data transfer using either full-rate or half-rate speech channels, where vacant frames in the traffic channel during discontinuous transmission are used for packet-switched data transmission, maintaining speech quality and increasing network capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If single-slot DTM uses half-rate speech channels, then simultaneous voice and data transfer is enabled in congested cells, but speech quality degrades
Solution Approach 1:
The system dynamically switches between half-rate and full-rate speech channels based on data traffic conditions. During active data transmission, half-rate speech is used to maximize capacity. When data transmission ceases, the system transitions to full-rate speech to maintain speech quality, making the speech rate adaptive rather than fixed
Solution Approach 2:
The system periodically alternates between speech and data transmission in a time-division manner. Speech transmission occurs in dedicated speech frames while data transmission occurs in data frames, creating a periodic pattern that allows both functions to coexist in a single timeslot without continuous degradation of speech quality
2Quantity of substance
If single-slot DTM is used in congested cells, then network capacity increases, but speech quality is reduced due to half-rate speech limitation
Solution Approach 1:
The speech channel dynamically adjusts its rate based on whether data transmission is active. The system monitors data traffic conditions and switches between half-rate and full-rate speech encoding, allowing the network to provide high capacity during data-intensive periods while restoring speech quality when data demands subside
Solution Approach 2:
The system changes the speech encoding parameters (rate) based on operational conditions. By transitioning between half-rate and full-rate speech modes, the system adapts the speech channel parameters to match current network demands, optimizing both capacity and quality
3Reliability
If full-rate speech channels are used with single-slot DTM, then speech quality is maintained, but simultaneous data transmission capability is lost
Solution Approach 1:
The system implements periodic time-division multiplexing where full-rate speech transmission alternates with data transmission in dedicated frames. This periodic structure ensures that speech quality is maintained during speech frames while data transmission capability is preserved during data frames, allowing both functions to coexist without compromising either
Data Source
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AI summary
The present document relates to radio transmission. In particular, the present document relates to the single-slot dual transfer mode (DTM) available e.g. in GSM/GPRS/GERAN networks. A transmitter is described. The transmitter is configured to send circuit switched data over a traffic channel to a corresponding receiver, wherein the traffic channel is segmented into a plurality of frames. The transmitter if further configured to determine a vacant frame of the plurality of frames, wherein no circuit switched data is sent in the vacant frame due to discontinuous transmission; and to send packet switched data over the traffic channel using the vacant frame.