EP1108342A1

EP1108342A1 - Method for transmitting voice information in a radiocommunication system

Info

Publication number: EP1108342A1
Application number: EP99953645A
Authority: EP
Inventors: Egon Schulz; Jürgen Schindler
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 1998-09-01
Filing date: 1999-09-01
Publication date: 2001-06-20
Also published as: CN1316170A; AU1029700A; WO2000013446A1

Abstract

The invention relates to a radio interface between a base station and a mobile station with broad-band channels that are sub-divided into time slots for the transmission of voice information. At least two data sequences are sent in one time slot. In a first group of time slots, both data sequences are allocated to a mobile station. In a second group of time slots, both data sequences are allocated to different mobile stations. Finer resource-unit granularity can be obtained by using several data sequences for one time slot. Hybrid-type allocation of one or two data sequences per time slot to a mobile station results in greater flexibility with respect to data throughput rates that can be allocated to a mobile station. This means that a greater number of spread CDMA subscriber-separation voice connections can be supported in TDD radiotelephone systems with broad-band channels.

Description

description

Method for the transmission of voice information in a radio communication system

The invention relates to a method for transmitting voice information in a radio communication system, in particular in m mobile radio systems with TDD subscriber separation.

In radio communication systems, messages (for example voice, image information or other data) are transmitted with the aid of electromagnetic waves via a radio interface. The radio interface relates to a connection between a base station and mobile stations, it being possible to supply fixed radio stations instead of the mobile stations. The electromagnetic waves are emitted at carrier frequencies that lie in the frequency band provided for the respective system. For future radio communication systems, for example the UMTS (Universal Mobile Telecommunication System) or other 3rd generation systems, frequencies in the frequency band of approx. 2000 MHz are provided.

DE 198 17 771 and DE 198 20 736 disclose radio communication systems with a TDD (time division duplex) subscriber separation, which have been optimized in the 3rd generation of a mobile radio system for high-rate data services. High-speed data services, e.g. for video and multimedia applications have the consequence that broadband channels with 5 MHz and e.g. 8 spreading codes were selected per time slot. This creates the smallest assignable resource unit of approx. 27.6 Kbit / s, which is very large.

According to the invention, such a radio communication system optimized for high-rate data services is also to be improved for the transmission of voice information. To do this, a Method with αen features of claim 1 specified, which also enables a high system capacity for the transmission of voice information. Further developments of the invention can be found in the subclaims.

According to the invention, a radio interface is provided between a base station and mobile stations with broadband channels divided into m time slots for the transmission of the voice information. At least two data sequences are transmitted in one time slot, with m data sequences of a mobile station being assigned to a first group of time slots and both data sequences being assigned to different mobile stations in a second group of time slots. The use of several data sequences per time slot results in a finer granularity of the

Resource units that were used in DE 198 17 771 only to signal a resource request. The mixed form of assigning one or two data sequences per time slot to a mobile station creates greater flexibility with regard to the data rate that can be assigned to a mobile station. A large number of voice connections of sufficient quality can thus be supported. This increases the system capacity for voice connections.

The method according to the invention finds particularly advantageous applications in radio communication systems in which a TDD subscriber separation method and / or additionally a subscriber separation are used by assigning different spreading codes to mobile stations of a time slot.

Different allocation methods are advantageously used in the upward and downward direction. On the one hand, radio blocks with a midamble embedded between the two data sequences will be sent in the downward direction. The data sequences before and after the midamble can therefore be one Be sen mobile station or two different mobile stations zugewie ^¬. On the other hand, m the uplink direction per time ^¬ be slit either sent a long radio block from a mobile station or two short temporally orthogonal radio blocks of zwe un- terschiedlichen mobile stations, wherein a long radio block represents only two data sequences and each short radio block data sequences. Since no common midamble can be transmitted synchronously with two different transmitters, each of the short radio blocks consists of a midamble and data parts. For the purposes of the invention, the two form

Data parts of a short radio block a data sequence. The channel estimation and data detection is simplified by this transmission of the data sequences, which is adapted to the downward and upward direction.

In order to support the voice transmission with a continuous flow of information, a mobile station is allocated on average between half and a resource unit, a resource unit being formed by the bandwidth, a spreading code and a time slot per frame. By means of a mixed assignment of one or two data sequences in one time slot, adjustable fractions of a resource unit can also be assigned. The fraction is set by the rotation of no, one or two data sequences per mobile station and the rotation cycle. A particularly significant fraction is 2/3 of a resource unit, i.e. e.g. three mobile stations share two resource units. Accordingly, a time slot with both data sequences is assigned to a mobile station in every third frame and a time slot with only one data sequence is assigned to m two out of three frames.

Exemplary embodiments of the invention are explained in more detail with reference to the accompanying drawings.

Show

1 shows a block diagram of a mobile radio system, 2 shows a schematic representation of the frame structure of the TDD transmission method, FIG 3 is a schematic representation of a long radio blocks ^¬, FIG 4 is a schematic representation of a short radio blocks, FIG 5 is a schematic representation of the transfer m

Upward direction, and FIG 6 is a schematic representation of the transmission in the downward direction.

The mobile radio system shown in FIG. 1 as an example of a radio communication system consists of a multiplicity of mobile switching centers MSC which are networked with one another or which provide access to a fixed network PSTN. Furthermore, these mobile switching centers MSC are each connected to at least one device RNM for allocating radio resources. Each of these RNM devices in turn enables a connection to at least one base station BS. Such a base station BS can connect to other radio stations, e.g. Set up mobile stations MS or other mobile and stationary devices. At least one radio cell is formed by each base station BS.

1 shows connections VI, V2, V3 for the transmission of useful information and signaling information between mobile stations MS and a base station BS as examples. An operation and maintenance center OMC implements control and maintenance functions for the mobile radio system or for parts of it. The functionality of this structure can be transferred to other radio communication systems in which the invention can be used, in particular for subscriber access networks with a wireless subscriber line.

The frame structure of the radio transmission is shown in FIG 2. According to a TDMA component (time division multiple access), a division of a broadband frequency range, for example the bandwidth B = 5 MHz m, into several time slots ts of the same duration, for example 16 time slots tsO to tsl5. A frequency band extends over a frequency range B. Some of the time slots ts0 to ts8 are used in the downward direction DL and some of the time slots ts9 to tsl5 are used in the upward direction UL. In between is a switch point SP. In this TDD transmission method, the frequency band for the upward direction UL corresponds to the frequency band for the downward direction DL. The same is repeated for other carrier frequencies.

Information from several connections is transmitted in the radio blocks within the time slots. The data d are spread individually for each connection with a fine structure, a spreading code c, so that, for example, n connections can be separated at the receiving end by this CDMA component. A resource unit, i.e. a physical channel Kl is formed by a frequency band B, a time slot ts and a spreading code c. The spread of individuals

Symbols of the data d have the effect that Q chips of the duration T _{chιP are} transmitted within the symbol duration Tsy _m . The Q chips form the connection-specific spreading code c.

Within a broadband frequency range B, the successive time slots ts are structured according to a frame structure. So 16 time slots ts are combined into a frame for.

The parameters of the radio interface are advantageously:

Chip rate: 4,096 Mcps

Frame duration: 10 ms

Number of time slots: 16 Duration of a time slot: 625 μs

Spread factor: 16

Modulation type: QPSK Bandwidth: 5 MHz

Repeat frequency value: 1

These parameters enable the best possible harmonization with an FDD mode (frequency diVision duplex) for the 3rd generation of mobile communications.

According to the invention, two types of radio blocks are used. According to FIG. 3, a long radio block MB, which fills an entire time slot ts, consists of a central amble MA, which is surrounded by two data sequences D1 and Dl. Furthermore, a protection time SP follows, which serves to compensate for differences in runtime.

A short radio block HB is also constructed, but it only takes up about half the time of a time slot ts. A first short radio block HB according to FIG. 4 with two data parts D1 'and Dl' ', which form a first data sequence Dl, becomes orthogonal in time within the time slot to a second short radio block HB with two data parts D2' and D2 '', the second Form data sequence D2, sent. Both short radio blocks HB are sent by different stations.

According to the specified parameters of the radio interface, a resource unit is a physical channel K1 with a data rate of 27.6 Kbit / s. The number of participants with this lowest data rate would also be limited by the number of physical channels. According to the invention, a lower data rate can be set for voice transmission by assigning less than one resource unit to a mobile station MS on average over time. In spite of this, the continuous data stream is simulated in contrast to a packet transmission, although the frame rate of a mobile station MS is not always the same data rate, but a varying data rate is available. In the upward direction UL, radio blocks from different mobile stations MSI, MS2, MS3 are sent to the base station BS. According to FIG 5, the time slots tsO, tsl are used for three voice connections of the mobile stations MSI, MS2, MS3. In the first time slot tsO, a long radio block is transmitted in rotation from one of the three mobile stations MSI, MS2, MS3, which means that each mobile station MSI, MS2, MS3 is assigned 1/3 of a resource unit. In the second time slot tsl, two short radio blocks HB are sent by the two mobile stations MSI, MS2, MS3 not transmitting in the first time slot tsO. The mobile stations MSI, MS2, MS3 thus have a further 1/3 resource unit available through the short radio blocks HB distributed over two frames frl. The long and short radio blocks MB, HB are spread according to FIG. 5 with different spreading codes cl, c2. However, due to the time separation according to time slots tsO, tsl, this is not an inevitable condition.

A part of the speech information is sent in each frame for, which means that the intermediate storage effort can be kept low. Both types of radio blocks should not be used at the same time in a time slot ts in order to keep the evaluation effort low on the receiving side, in particular in the case of channel estimation.

For example, the first mobile station MSI uses a long radio block MB in the first frame frl and its two data sequences D1, D2 and m use the two following frames fr2, fr3 each a short radio block HB and thus the two data parts Dl 'and Dl' ' first sequence D1. This mobile station MSI thus has a data rate of 18.4 Kbit / s available.

In the downward direction DL according to FIG. 6, the base station BS transmits to several mobile stations MSI, MS2, MS3. Only long radio blocks HB are used, so it is possible but not necessary that only one time slot tsO is used in the sense of rotation with two different spreading codes cl, c2.

The base station transmits for the three mobile stations MSI, MS2, MS3 rotating two Datensequen ^¬ zen Dl and D2, thereby averaged over time, in turn, each of the three mobile stations MSI, MS2, MS3, a 1/3 resource unit communicates with the first spreading code Cl for disposal. A second long radio block MB is sent spread with the second spreading code c2, the second mobile station MS2 evaluating the first data sequence D1 and the third mobile station MS3 the second data sequence D2 in the first frame frl. Here, too, there is a rotation across the frames frl, fr2, fr3 .., as a result of which a further 1/3 resource unit is available to each of the mobile stations MSI, MS2, MS3.

The exemplary embodiment showed how three mobile stations MSI, MS2, MS3 share two resource units. However, it is within the scope of the invention that other fractions can also be set by means of a corresponding rotation sequence. Likewise, the rotation can be carried out without the use of different spreading codes cl, c2 by sending m different time slots tsO, tsl, possibly with the same spreading code cl.

Claims

claims

1. A method for transmitting voice information in a radio communication system, in which a radio interface between a base station (BS) and mobile stations (MS) is provided with broadband channels divided into time slots (ts) for transmitting the voice information, in a time slot (ts ) At least two data sequences are sent, both data sequences (Dl, D2) of a mobile station (MSI) in a first group of time slots (tsl) and both data sequences (Dl, D2) of different mobile stations in a second group of time slots (ts2) (MS2, MS3) can be allocated.

2. The method as claimed in claim 1, in which part of the time slots (ts) of a frame are used according to a TDD subscriber separation method for the uplink (UL) and another part of the time slots (ts) for the downlink (DL).

3. The method according to any one of the preceding claims, in which a subscriber separation is additionally carried out by assigning different spreading codes (c) to mobile stations (MS) of a time slot (ts).

4. The method according to any one of the preceding claims, in which in downward direction (DL) radio blocks with a between the two data sequences (Dl, D2) embedded midamble (MA) are sent.

5. The method according to any one of the preceding claims, in which in the upward direction (UL) per time slot (ts) either one long radio block (MB) from a mobile station (MSI) or two short temporally orthogonal radio blocks (HB) from two different mobile stations (MS2, MS3) are sent, with a long radio block (MB) two data sequences (Dl, D2) and each short radio block (HB) represents only one data sequence (D1, D2).

6. The method according to any one of the preceding claims, wherein a resource unit is formed by the bandwidth, a spreading code and a time slot (ts) per frame and a mobile station (MS) by a mixed assignment of one or two data sequences (Dl, D2) in a time slot is assigned on average between half a unit of resources and one.

7. The method as claimed in claim 6, in which a mobile station (MS) has a time slot (tsl) with both data sequences (Dl, D2) every third frame and a time slot (ts2) with only one data sequence (Dl, D2) in two of three frames. is assigned.