Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
1998-02-06
2001-09-18
Hunter, Daniel (Department: 2684)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S452200, C455S063300, C455S067150, C455S067700, C455S071000, C455S450000
Reexamination Certificate
active
06292664
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates in general to the wireless communication systems field, and in particular, to a method and system for improving channel quality in wireless communication systems.
2. Description of Related Art
Benefits of mobile wireless communications are safety, convenience, and efficiency. To maximize the enjoyment of these benefits, the quality of transmitted voice signals should be optimized. Voice quality in today's digital communication systems depends primarily on the coding process employed to digitize speech. One parameter affecting voice quality is the number of bits per second transmitted by a given speech coding technique (e.g., using vocoders, waveform coders, hybrid coders, etc.). Generally, the higher the bit rate, the better the voice quality.
Unfortunately, as the bit rate is increased, the transmission bandwidth demanded by the speech coding technique is also increased. In a cellular wireless communications system, the transmission bandwidth between the mobile terminals and a base station is finite. This finite transmission bandwidth is best utilized in existing cellular systems by assigning channels that can accommodate the speech coding technique with the lowest-possible bit rate.
A conventional traffic channel assignment method is for a base station to receive a request from a mobile terminal for a traffic channel. The associated cellular system then determines the lowest-possible traffic bit rate. The mobile terminal's call is then assigned to a channel that uses the lowest-possible traffic bit rate.
The problem with the existing cellular systems is that the lowest-possible traffic rate channel often corresponds to the use of a sub-optimum speech coding technique. In other words, the associated cellular system requires the use of a speech coding technique with fewer bits per second, in order to minimize the amount of the total available bandwidth occupied by a single call from a mobile terminal. Unfortunately, reduced speech quality accompanies the use of a lower-rate speech coding technique. Furthermore, existing cellular systems typically select a lower-rate speech coding technique for a call even when significant bandwidth capacity in a given cell is available. For example, a half-rate traffic channel is used to gain capacity in the network, and today a half-rate channel is always assigned when the mobile terminal is capable of half-rate, the call is between the mobile terminal and the Public Switched Telephone Network (PSTN), and the call is a speech call.
In summary, conventional traffic channel assignment methods assign the lowest-possible traffic rate channel to a mobile terminal at the expense of transmitted voice quality.
SUMMARY OF THE INVENTION
The present invention provides a method and system for assigning premium traffic channels to mobile terminals that request calls. In accordance with the present invention, each cell in a communications system is assigned a predetermined High Traffic Threshold (HTTH) value. The HTTH value can be defined, for example, as an absolute number of channels in use, or a ratio of the channels in use to the total channels provided in the cell. According to a first embodiment, call requests from mobile terminals are assigned premium (e.g., higher bit rate) traffic channels until the occupied capacity of the cell reaches the HTTH value. Thereafter, mobile terminals are assigned traffic channels that provide a lower speech quality.
In a second embodiment, a first speech coding technique is provided that uses a predetermined number of bits for digitizing a voice signal. A second speech coding technique uses half the predetermined number of bits; consequently, voice quality using the first technique is superior. When a base station receives a request from a first mobile terminal for a traffic channel while occupied capacity is below the HTTH value, a traffic channel using the first speech coding technique is assigned by, for example, an associated Mobile services Switching Centre (MSC). Alternatively, when a base station receives a request from a second mobile terminal for a traffic channel after occupied capacity has exceeded the HTTH value, a traffic channel that corresponds to the second speech coding technique is assigned as the call situation permits.
An important technical advantage of the present invention is that it enables intelligent traffic channel selection.
Another important technical advantage of the present invention is that it provides efficient use of available wireless communication bandwidth.
Yet another important technical advantage of the present invention is the ability to adjust the selected speech coding technique, and thus the transmitted voice quality, based on the current occupied cell capacity.
Yet another important technical advantage of the present invention is the ability to improve voice quality for users when the cell is operating at less than full-capacity.
The above-described and other features of the present invention are explained in detail hereinafter with reference to the illustrative examples shown in the accompanying drawings. Those skilled in the art will appreciate that the described embodiments are provided for purposes of illustration and understanding and that numerous equivalent embodiments are contemplated herein.
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Andersson Mikael
Ostrup Peter
Westroos Anders Kjell
Hunter Daniel
Jenken & Gilchrist, P.C.
Telefon Aktiebolaget LM Ericsson (publ)
Woldetatios Yemane
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