Method, System and Apparatus for Providing Modulation and Coding Mode used by Multicast Service Macro Diversity

Abstract

A method, system and apparatus are provided for modulation and coding mode used by multicast service macro diversity. A message containing relevant information of modulation and coding mode(s) used by an MBS zone is sent in the MBS zone. The MS receives the message, analyzes other messages in the MBS zone according to the relevant information of the modulation and coding mode(s) contained in this message, and receives MBS service data according to the analyzed result upon other messages in the MBS zone. The invention resolves the problem that an entity is required to uniformly manage the coding and modulation mode definition of each cell in the prior art, as well as the problem that the DCD count in the DL-MAP message has to be continuously tracked in the prior art.

Description

BACKGROUND OF THE INVENTION

1. Field of the Technology

The invention relates to multicast service macro diversity techniques, more particularly to a method, a system and apparatus for providing modulation and coding mode used by multicast service macro diversity.

2. Field of the Invention

With the rapid development of the Internet, a multitude of multimedia services have emerged, some of which require the same data to reach multiple users at the same time, namely to be multicast, and such services may be video on demand, television on demand, video conference, online education, interactive games and so on.

3. Background of the Invention

Multicast is a technique that transfers data from one data source to multiple destinations, including multicast and broadcast. As to broadcast services, Cell Broadcast Service (CBS) in traditional mobile networks only allows transmitting low-bit-rate data to all users through the cell's shared broadcast channel, which belongs to message services. As to multicast services, there are IP multicast techniques in terms of the existing IP networks, but the mobile network has some characteristics different from those of IP network, such as network structure, function entities and wireless interfaces, so the current IP multicast techniques are not applicable for mobile networks. In addition, compared with common services, mobile multimedia services are of the characteristics such as large quantity of data, long time duration, delay sensitive and so on. Therefore, transmission using current techniques of broadcast services and multicast service are not suitable for data transmission of mobile multimedia services.

In order to effectively utilize wireless resources, the Third Generation Partnership Project (3GPP), which is a Wideband Code Division Multiple Access/Global System for Mobile Communications (WCDMA/GSM) global standardization organization, provides Multimedia Broadcast/Multicast Service (MBMS), and on the other hand, Multicast and Broadcast Service (MBS) is introduced into the latest protocol IEEE802.16e/D5 of IEEE802.16. MBMS service and MBS service provide the specifications of multicast in the mobile networks, so that a mobile network can provide point to multipoint services, thereby network resources can be shared, utilization ratio of network resources, especially of the air interface, is increased. The newly provided MBMS and MBS service can realize multicast and broadcast of both low-bit-rate text messages and high-bit-rate multimedia services, and this is obviously the trend of future mobile traffic development.

The network structure of the MBS service in IEEE802.16 protocol is shown in FIG. 1. With reference to FIG. 1, a mobile network function entity, MBS server 100, is newly added to support MBS service, one function of MBS server 100 is to act as entry of content providers, and another is to manage multicast data transmission of the Base Stations (BSs) 200 belonging to the MBS server 100, as well as distribute multicast data to those BSs. In addition, function entities like Mobile Stations (MSs) 300 and BSs 200 need to be mended by adding MBS service-relevant functions.

The MBS service operation mainly includes following steps: obtaining MBS service list information, MBS service authentication and obtaining the key, and normally receiving the MBS service. Specifically, before normally receiving the MBS service, MS acquires information, such as MBS content list, from MBS server first, and then requests a BS to authenticate the received MBS service content; after successful authentication, the BS transmits MBS downlink service parameters and other information to the MS, the MS then requests the BS to return the MBS key. When receiving the downlink service parameters and MBS key, the MS can receive related Media Access Control Protocol Data Unit (MAC PDU) and begin to receive the MBS service normally.

As mentioned above, normally receiving MBS service mainly means receiving MBS service content with the received MBS downlink service parameters. In the current standard draft, MBS downlink service parameters mainly include MBS ZONE identifier and Multicast Connection ID (Multicast CID).

In order to support macro diversity, which can improve the receiving performance, MBS-MAP message is introduced into IEEE802.16e/D5, the latest edition of IEEE802.16, this message is transmitted in MBS ZONE and its Information Elements (IEs) are shown as table 1.

TABLE 1
Syntax	Size	Notes
MBS-MAP_Message_Format( ) {
Management Message Type = ?	8 bits
Frame number	24 bits	The frame number is identical to the frame number
		in the DL-MAP
for (I = 0; i < n; i++) {
Multicast CID	12 bits	12 LSB of CID for multicast
Modulation and Coding mode (DIUC)	4 bits
OFDMA Symbol offset	8 bits	OFDMA symbol offset with respect to start of the
		MBS zone
Subchannel offset	6 bits
Power Offset (Boosting)	3 bits	000: normal (not boosted); 001: +6 dB; 010: −6 dB;
		011: +9 dB; 100: +3 dB; 101: −3 dB; 110: −9 dB; 111:
		−12 dB;
No. OFDMA Symbols	7 bits
No. Subchannels	6 bits
Repetition Coding Indication	2 bits	0b00 - No repetition coding
		0b01 - Repetition coding of 2 used
		0b10 - Repetition coding of 4 used
		0b11 - Repetition coding of 6 used
Next MBS frame offset	8 bits	The Next MBS frame offset value is lower 8 bits
		of the frame number in which the BS shall transmit
		the next MBS frame.
Next MBS OFDMA Symbol offset	8 bits	The offset of the OFDMA symbol in which the
		next MBS zone starts, measured in OFDMA
		symbols from the beginning of the downlink frame
		in which the MBS-MAP is transmitted.
}
If !(byte boundary) {
Padding Nibble	4 bits	Padding to reach byte boundary.
}
}

The MBS-MAP message is used to notify each Multicast CID in the MBS ZONE of the physical channel resources allocated for them, including modulation and coding mode(s) of the burst, which is (are) indicated by a Downlink Interval Usage Code (DIUC), power offset, which is indicated by Boosting, and position of the next MBS frame. Therefore, if it correctly detects the MBS-MAP message, an MS can obtain the expected burst corresponding to the multicast connection, and the modulation and coding mode(s) used on the burst, and the power offset etc, then determines the position of the next MBS frame in this multicast connection, thereby normally receives the data through the multicast connection.

In the MBS-MAP message, the information element (IE) of DIUC is a 4-bit identifier used to identify the modulation and coding mode(s) used by current burst, and each form of the 4-bit identifier represents one kind of modulation and coding mode. Thus the 4-bit identifier is also called a “DIUC index,” i.e., an index of modulation and coding modes. This DIUC value is defined in the Downlink Channel Description (DCD) message which is periodically broadcast by the current cell. Any change of the DCD message is identified by the Configuration Change Count in the DCD message and traced by using DCD count in other related information. For instance, DCD count is used in a Downlink Map (DL-MAP) message to track changes of the DCD message.

In cellular systems, users at the edge of a cell endure poor communication qualities due to their long distance to the BS. In an effort to overcome this problem, macro diversity is introduced into cellular systems. With macro diversity, a receiver can receive signals from surrounding base stations, and extract useful signals from the received signals, thereby avoiding poor communication quality due to receiving signals from the single BS.

Moreover, when receiving the MBS service, a receiver needs to continuously track the DL-MAP message in order to track the change of the DCD count, so as to determine whether to receive a new DCD message or not, irrespective of whether the receiver is in SLEEP state or IDLE state, which is obviously a waste of power.

SUMMARY OF THE INVENTION

In view of the above, embodiments of the invention provide a method, a system and apparatus for providing a modulation and coding mode used by multicast service macro diversity, so as to provide the modulation and coding mode used by multicast service macro diversity for the MBS service with less system cost.

Embodiments of the invention also provide a method, a system and apparatus for providing a modulation and coding mode used by multicast service macro diversity, so that the receiver needs not continuously track the DL-MAP message.

According to one embodiment of the invention, a method for providing modulation and coding mode information used for multicast service macro diversity is provided, which includes: sending, by a base station, a message which defines DIUC-relevant information of modulation and coding mode(s) indicated by a downlink interval usage code (DIUC) and used in a multicast and broadcast service (MBS) zone; wherein said message is contained in the MBS zone of a downlink frame.

According to the other embodiment of the invention, a method for providing modulation and coding mode used by multicast service macro diversity is provided, which includes sending, by a base station, a downlink channel description (DCD) message defining DIUC-relevant information of a downlink interval usage code (DIUC) used by a downlink burst; and sending, by the base station, a MBS-MAP message in a multicast and broadcast service (MBS) zone comprising an information element (IE) indicating the update of the DCD message.

According to another embodiment of the invention, a base station is provided, which includes a transmitter, configured to send a message which defines DIUC-relevant information of modulation and coding mode(s) indicated by a downlink interval usage code (DIUC), and configured to send a multicast and broadcast service map (MBS-MAP) message in a multicast and broadcast service (MBS) zone; the MBS-MAP message comprising an information element (IE) indicating an update of the message.

According to yet another embodiment of the invention, a mobile station (MS) for receiving multicast and broadcast service (MBS) data is provided, which includes: a receiver, configured to receive a message which defines DIUC-relevant information of modulation and coding mode(s) indicated by a downlink interval usage code (DIUC), and to receive a multicast and broadcast service map (MBS-MAP) message in a multicast and broadcast service (MBS) zone, the MBS-MAP message comprising an information element (IE) indicating the update of the message; the receiver further configured to receive the MBS data according to the DIUC-relevant information of modulation and coding mode(s) contained in the message.

In the solution of the invention, a MBS-DCD message containing the definition and index of the modulation and coding mode used by MBS ZONE is added into the MBS ZONE, the MS receives the downlink MBS service according to the definition and index contained in this message. Transmission of the added MBS-DCD message is specified in the MBS-MAP message, wherein the MBS-MAP message is transmitted by MBS Server, so that the added MBS-DCD messages are uniformly managed by MBS Server in the MBS ZONE, without the need of introducing a new entity to uniformly manage the DCD messages of all cells in the same MBS ZONE as in the prior art.

In the embodiments of the invention, the MBS-MAP message is enhanced by adding an IE indicating the DCD message update, so that the MS can judge whether to receive the new DCD message according to the fact whether this IE is identical to the corresponding IE in the current DCD message reserved by itself, thereby the MS need not continuously track the DL-MAP message, unless it is detected that the IE of MBS-MAP message is not identical to the corresponding IE in the current DCD message reserved by itself. Thus the receiver in IDLE state or SLEEP state need not continuously monitor the DL-MAP message of current service cell and power consumption of the MS is reduced.

In the embodiments of the invention, by setting MBS-DCD message in MBS ZONE and enhancing the MBS-MAP message, the MBS-DCD messages in MBS ZONE are uniformly managed through the MBS Server and there is no need to introduce a new entity to uniformly manage the DCD messages of all cells in the same MBS ZONE, and the MS can determine whether to receive the new MBS-DCD message by judging whether the IE, which is added into the MBS-MAP message and is used to indicate the MBS-DCD message update, is identical to the corresponding IE in the current MBS-DCD message reserved by itself, so that the MS need not to continuously track the DL-MAP message, so that the receiver in IDLE state or SLEEP state need not continuously monitor the DL-MAP message of current service cell and power consumption of the MS is reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating a system structure supporting the MBS service in IEEE802.16 in the prior art;

FIG. 2 is a diagram showing the sequence of transmission of downlink and uplink frames respectively;

FIG. 3 is a diagram showing the main components of a downlink frame;

FIG. 4 is a simplified block diagram of a base station, illustrating frame memories in which the data is assembled before transmission;

FIG. 5 is a diagram showing the arrangement of data, in accordance with an embodiment of the invention, as stored in the frame memories in the base station illustrated in FIG. 4;

FIG. 6 is a diagram showing and MBS-MAP message included in the data illustrated in FIG. 5;

FIG. 7 is a diagram showing in MBS-DCD message included in the data illustrated in FIG. 5;

FIG. 8 is a simplified block diagram of the main components of a mobile station for receiving downlink frames constructed as illustrated in FIGS. 5, 6 and 7; and

FIG. 9 is a block diagram illustrating components of the MBS server which controls the organization of the data in the MBS zone of the downlink frame and the coding and modulation modes which are employed for that data.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Various features and aspects of the invention will be described in detail hereinafter with reference to specific embodiments and to the accompanying drawing figures.

In operation of the cellular telecommunications system shown in FIG. 1, information is transmitted from the base stations BS to the mobile stations MS in a series of spaced apart downlink frames 10, as shown in FIG. 2. Information from the mobile stations MS to the base stations BS is transmitted in a series of spaced apart uplink frames 12. Also as illustrated in FIG. 2, the downlink frames 10 and uplink frames 12 are transmitted alternately.

As illustrated in FIG. 3, each downlink frame 10 is divided into three main time periods 14, 16 and 18. The time period 14, which is at the beginning of the frame, contains a conventional preamble and need not be described further. The second time period 16 follows the preamble period 14 and contains traffic data, such as digital data representing voice telephone calls. The third time period 18 which is known as the MBS zone follows the traffic period 16 and contains multicast and broadcast data. As shown in FIG. 3, the time periods 14, 16 and 18 may, by way of example, have a duration, respectively, of 1 ms, 7 ms and 2 ms. Further, the MBS zone 18 is not necessarily present in all downlink frames.

As will be explained more fully later, the data transmitted in the traffic period 16 and the MBS zone 18 is organized in bursts which may be encoded and modulated by coding and modulation modes which may differ from one burst to another in the same downlink frame and/or may differ from one downlink frame to the next. To enable the mobile stations MS to decode and demodulate the bursts, therefore, it is necessary to transmit to the mobile station MS data identifying the modulation and coding modes which have been employed in the transmitted bursts. This data comprises a DIUC definition (downlink interval usage code definition) which lists the identities of the coding and modulation modes currently available for use in the downlink frames and a DCD count (downlink channel description) which is incremented each time the DIUC definition changes so as to notify the mobile station of this change.

The first embodiment of the invention is to add an MBS-DCD message, i.e. a DIUC value, in the MBS ZONE to define the modulation and coding mode used in current MBS ZONE. The structure of the defined MBS-DCD message is as shown in table 2.

TABLE 2
Syntax	Size	Notes
MBS-DCD_Message_Format( ) {
Management Message Type = ?	8 bits	MBS_MAP = 0x05
Begin PHY Specific Section {		See applicable PHY section
for (I = 1; i <= n; i++) {		For each downlink burst profile
		1 to n
Downlink_Burst_Profile		PHY specific
}
}
}

Wherein, the definition of Downlink_Burst_Profile in Table 2 is given in chapter 11.4.2 of IEEE802.16-2004, in the MBS-DCD message, Downlink_Burst_Profile defines the specific meaning of each 4-bit DIUC index.

In addition, as other messages set in the MBS ZONE, transmitting position of the MBS-DCD message should be specified in the MBS-MAP message.

When receiving MBS service, the MS determines the position of MBS-MAP message, and tracks this message until the corresponding MBS-DCD message is correctly received. The MS then analyzes other messages in the MBS ZONE with relevant description upon DIUC in the MBS-DCD message, and receives the downlink MBS service according to the analyzed result.

In the present embodiment, an MBS-DCD message containing the definition and index of the modulation and coding mode used in MBS ZONE is added into the MBS ZONE, according to the definition and index of the modulation and coding mode contained in the message, the MS receives the downlink MBS service. The transmission of the added MBS-DCD message is specified in the MBS-MAP message that is sent by the MBS Server, and the MBS-DCD message is uniformly managed by the MBS Server in the MBS ZONE. Accordingly, there is no need to introduce a new entity to uniformly manage the DCD messages of all cells in the same MBS ZONE, as required in the prior art.

The second embodiment of the invention improves the current MBS-MAP message so as to track the change of DCD message. An IE of DCD count is added into the MBS-MAP message, so that the update of DCD message can be recorded by this IE. The IEs of the improved MBS-MAP message is as shown in FIG. 3.

TABLE 3
Syntax	Size	Notes
MBS-MAP_Message_Format( ) {
Management Message Type = ?	8 bits
DCD count	8 bits
Frame number	24 bits	The frame number is identical to the frame number
		in the DL-MAP
for (i = 0; i < n; i++) {
Multicast CID	12 bits	12 LSB of CID for multicast
DIUC	4 bits
OFDMA Symbol offset	8 bits	OFDMA symbol offset with respect to start of the
		MBS zone
Subchannel offset	6 bits
Boosting	3 bits	000: normal (not boosted); 001: +6 dB; 010: −6 dB;
		011: +9 dB; 100: +3 dB; 101: −3 dB; 110: −9 dB;
		111: −12 dB;
No. OFDMA Symbols	7 bits
No. Subchannels	6 bits
Repetition Coding Indication	2 bits	0b00 No repetition coding)
		0b01 Repetition coding of 2 used)
		0b10 Repetition coding of 4 used)
		0b11 Repetition coding of 6 used)
Next MBS frame offset	8 bits	The Next MBS frame offset value is lower 8 bits of
		the frame number in which the BS shall transmit
		the next MBS frame.
Next MBS OFDMA Symbol offset	8 bits	The offset of the OFDMA symbol in which the next
		MBS zone starts, measured in OFDMA symbols
		from the beginning of the downlink frame in which
		the MBS-MAP is transmitted.
}
if !(byte boundary) {
Padding Nibble	4 bits	Padding to reach byte boundary.
}
}

In this way, when receiving the MBS-MAP message, the MS checks whether the carried DCD count is identical to the Configuration Change Count reserved in the current DCD message, and if identical, the MS receives the MBS service normally; otherwise, the MS tracks the DCD message until the Configuration Change Count contained in the new received DCD message is identical to the DCD count in the MBS-MAP message. Then the MS analyzes other messages in the MBS ZONE according to the relevant description upon DIUC message in this new DCD message, and receives the downlink MBS service according to the analyzed result.

In the present embodiment, the MBS-MAP message is improved by adding an IE indicating the update of MBS-DCD message. With the improved MBS-MAP message, the MS can decide whether to receive the new DCD message according to the fact whether this IE is identical to the corresponding IE in the current DCD message reserved by the MS. If the IE is determined to be identical to that embedded in the MBS-MAP message, the MS need not continuously track the DL-MAP message. However, if it is determined that the IE of the MBS-MAP message is not identical to the counterpart in the current DCD message reserved by the MS, the receiver can be in IDLE mode or SLEEP mode need not continuously monitor the DL-MAP messages of the current service cell, and power consumption of the MS can be reduced, thereby preserving battery life.

The third embodiment of the invention is to add an MBS-DCD message, i.e., a DIUC value, in the MBS ZONE at first to define the modulation and coding mode used in current MBS ZONE. The MBS-DCD message is as shown in table 4.

TABLE 4
Syntax	Size	Notes
DCD_Message_Format( ) {
Management Message Type = ?	8 bits	MBS_MAP = 0x05
Configuration Change Count	8 bits
Begin PHY Specific Section {		See applicable PHY section
for (i = 1; i <= n; i++) {		For each downlink burst
		profile 1 to n
Downlink_Burst_Profile		PHY specific
}
}
}

In this embodiment, the definition of Downlink_Burst_Profile is as described in chapter 11.4.2 of IEEE802.16-2004. Besides, the transmission position of MBS-DCD message is specified in the MBS-MAP message.

Meanwhile, the MBS-MAP message should be improved to track the change of MBS-DCD message. Therefore, a MBS-DCD count IE is added into the MBS-MAP message, which can indicate the update of the MBS-DCD message. The improved MBS-MAP message is as shown in Table 5.

TABLE 5
Syntax	Size	Notes
MBS-MAP_Message_Format( ) {
Management Message Type = ?	8 bits
MBS-DCD count	8 bits
Frame number	24 bits	The frame number is identical to the frame number in the
		DL-MAP
for (i = 0; i < n; i++) {
Multicast CID	12 bits	12 LSB of CID for multicast
DIUC	4 bits
OFDMA Symbol offset	8 bits	OFDMA symbol offset with respect to start of the MBS zone
Subchannel offset	6 bits
Boosting	3 bits	000: normal (not boosted); 001: +6 dB; 010: −6 dB; 011:
		+9 dB; 100: +3 dB; 101: −3 dB; 110: −9 dB;
		111: −12 dB;
No. OFDMA Symbols	7 bits
No. Subchannels	6 bits
Repetition Coding Indication	2 bits	0b00 No repetition coding
		0b01 Repetition coding of 2 used
		0b10 Repetition coding of 4 used
		0b11 Repetition coding of 6 used
Next MBS frame offset	8 bits	The Next MBS frame offset value is lower 8 bits of the
		frame number in which the BS shall transmit the next MBS
		frame.
Next MBS OFDMA Symbol offset	8 bits	The offset of the OFDMA symbol in which the next MBS
		zone starts, measured in OFDMA symbols from the
		beginning of the downlink frame in which the MBS-MAP is
		transmitted.
}
if !(byte boundary) {
Padding Nibble	4 bits	Padding to reach byte boundary.
}
}

After the setting, when receiving the MBS-MAP message, the MS checks whether the carried DCD count is identical to the Configuration Change Count reserved in the current DCD message. If identical, the MS will receive the MBS service normally; otherwise, the MS will continuously track the DCD message until the Configuration Change Count contained in the received new DCD message is determined to be identical to the MBS-DCD count in the MBS-MAP message. Then the MS will analyze other messages in the MBS ZONE according to the relevant description upon DIUC message in this new DCD message, and receive the downlink MBS service according to the analyzed result.

In the present embodiment, by setting the MBS-DCD message in MBS ZONE and improving the MBS-MAP message, it is realized that the MBS-DCD message in MBS ZONE is uniformly managed by the MBS Server, so that there is no need to introduce a new entity to uniformly manage the DCD messages of all cells in the same MBS ZONE. Further, the MS can determine whether to receive the new MBS-DCD message by the fact whether the IE, which is added into the MBS-MAP message and used to indicate the update of the MBS-DCD message, is identical to the corresponding IE reserved in the current MBS-DCD message. If such is the case, the MS need not continuously track the DL-MAP message, so that the receiver in IDLE state or SLEEP state need not continuously monitor the DL-MAP messages of current service cell and power consumption of the MS can be reduced.

Thus, by way of summary, the three embodiments of the invention which have been described above organize the DIUC definition and the DCD count in three different novel ways as follows:

1. In the first embodiment, the DIUC definition relating to the modulation and coding modes used for the bursts in the traffic period 16, and the corresponding DCD count, are both transmitted in the traffic period 16 and the DIUC definition which relates to the modulation and coding modes used for the bursts of the MBS zone 18 is transmitted in the MBS zone 18. There is no DCD count relating to the DIUC definition for the MBS zone 18. In this embodiment, mobile stations which are receiving only MBS data monitor the DIUC definition in the MBS zone 18 each frame containing an MBS zone, but they do not need to monitor the data transmitted in the traffic period 16.

2. In the second embodiment, the DIUC definition relating to the modulation and coding modes used for the bursts in both traffic period 16 and MBS zone 18 is transmitted within the traffic period 16 and the DCD count appears twice in each frame which contains an MBS zone, once in the traffic period 16 and once in the MBS zone 18. In this embodiment, mobile stations which are only receiving data in the MBS zone monitor the DCD count in the MBS zone each frame which contains an MBS zone, and they only have to monitor the data in the traffic period 16 when the DCD count changes indicating a change in the DIUC definition.

3. In the third embodiment, the DIUC definition relating to the MBS zone 18 and the corresponding DCD count are both transmitted in the MBS zone 18, and a DIUC definition relating to the traffic period 16 and related DCD count are both transmitted in the traffic period 16. In this embodiment, mobile stations receiving only MBS data do not have to monitor the traffic zone 16 at all. Instead, such MS monitor only the DCD count received in the MBS zone 18 each frame containing an MBS zone until this changes, at which time they monitor the new DIUC definition received in the MBS zone 18.

An implementation of the third embodiment will now be described in more detail with reference to FIGS. 4 to 9.

With reference to FIG. 4, the base station BS includes input circuitry 20 for receiving data from the backbone 2 or another source or sources such as the up-layer or Internet preprocessing components 22 for preprocessing the received data and supplying it to first and second frame memories 24, and output processing components 26 which receive data from the frame memories 24 and prepare it for transmission by a radio-frequency transmitter 28. The components 22 and 26 may be implemented in hardware and/or software as appropriate. The data received from the backbone 2 will in practice originate from a variety of sources but will typically comprise MBS data from the MBS server 4, data representing voice calls and data representing other messages. The preprocessing components 22 include an encoder and an interleaver so that, as is conventional, the data provided to each frame memory 24 is in the form of interleaved digital data symbols. These symbols are assembled in the frame memories 24 in a manner such that the downlink frames 10 are formed when the symbols are read out and processed by the components 26 in preparation for transmission. The arrangement is such that, as indicated by the arrows 23 and 25 in FIG. 4, while data from the preprocessing components 22 is being read into and assembled in one of the frame memories 24, data previously assembled in the other is read out to the output processing components 26.

Each frame memory 24 comprises a plurality of memory cells, each for containing a single data symbol, arranged in rows 30 and columns 32 as shown in FIG. 5, to form a rectangular array. The position of any data symbol within the frame memory 24 can accordingly be defined by identifying the row 30 and the column 32 at the intersection of which the relevant memory cell is located. As shown in FIG. 5, the rows are actually referred to as “subchannels”. This is because the output processing components 26 of the base station BS carry out an inverse fast Fourier transform such that each row is assigned to a different subchannel. As also shown in FIG. 5, the columns 32 are referred to as OFDMA (orthogonal frequency division multiple access) symbol offset numbers. Thus, the position of each data symbol can be defined by its subchannel number and its OFDMA symbol offset number.

The data symbols which constitute the preamble, the traffic and the MBS data are assembled in each frame memory 24 in three segments thereof labeled respectively 14′, 16′ and 18′ for consistency with FIG. 3. The segment 14′ is shown as occupying a single column corresponding to OFDMA symbol number 0, the segment 16′ is shown as occupying the columns corresponding to OFDMA symbol numbers 1 to M−1, and the segment 18′ is shown as occupying the columns from OFDMA symbol number M onwards. As already indicated, the preamble is conventional and need not be described further.

With continuing reference to FIG. 5, the segment 16′ contains, in the first few columns, a frame control header 34, a downlink map 36 and an uplink map 38. The remainder of the segment 16′ is occupied by a number of data bursts 40, the first of which identified as DL burst 1 contains the downlink channel description (DCD) message and the remainder of which contain traffic such as voice call data.

The segment 18′, identified as the MBS zone, contains, in this embodiment, an MBS-MAP message 42, which includes the MBS-DCD count, and a number of data bursts 44, the first of which contains the MBS downlink channel description (MBS-DCD) message.

The position and size of each burst 40, 44 when stored within the frame memory 24 can thus be defined by the subchannel number and OFDMA symbol offset number of its extreme upper left-hand symbol (as seen in FIG. 5) and the number of rows and columns (i.e., the number of subchannels and OFDMA symbols) over which it extends.

To enable a mobile station MS to decode the bursts 40 and 44, for the mobile stations to receive information which defines the position and size of each burst and the modulation and coding mode used for the burst. In this embodiment, this information is provided:

(a) in relation to the bursts 40 by the downlink map message 36 and the downlink channel description (DCD) message provided in the first burst (burst 1) of the bursts 40;

(b) in relation to the bursts 44 by the MBS-MAP message 42 and the MBS-DCD (MBS downlink channel description) message provided, in the MBS zone, in the first burst (burst 1) of the bursts 44.

As shown in FIG. 6, the MBS-MAP message comprises a table 46 having a number of lines each corresponding to a respective different one of the bursts 44. Each line contains the multicast CID (connection identifier) of the burst, the downlink interval usage code (DIUC) for the burst, which is an index number used for identifying the coding and modulation mode used for the burst, and the position and size of the burst defined as described above by the position of the top left-hand corner of the burst (as seen in FIG. 5) in terms of OFDMA symbol offset and subchannel number and the number of subchannels and OFDMA symbols over which it extends.

At any given time, a subset of all of the possible modulation and coding modes will be available for use and, from time to time, the available modes will change. To indicate when a change in the available modes arises, the MBS-MAP message also includes an MBS-DCD count 48, which is a number which is incremented by one each time there is a change in the available subset of modulation and coding modes.

The subset of currently available coding and modulation modes is identified in a look-up table 50 as shown in FIG. 7, which constitutes the MBS-DCD message which is, as already indicated, contained in the first of the bursts 44. Table 50, as shown in FIG. 7, contains a list of the identities of the currently available modulation and coding modes, identified as mode 1, mode 2 . . . etc., and, next to the identity of each mode, the DIUC index number which relates to it. Thus, the receiver, when processing the MBS-MAP message, uses the DIUC index number relating to each burst in order to obtain, from the look-up table 50, the identity of the modulation mode for the burst.

It follows that when a mobile station MS is receiving MBS messages, the MS can detect a change in the available subset of modulation and coding modes by simply monitoring the MBS-DCD count 48 in the MBS-MAP message. When the MS detects that this count is changed, the MS can receive and decode the new MBS-DCD message containing the new available subset of the modulation and coding modes. Thus, as shown in FIG. 8, the mobile station MS includes a transmission information store 52 for storing the MBS-MAP message 42 and MBS-DCD message 50 and a sleep mode controller 54 which, in dependence upon the information in the transmission information store 52, may cause the RF receiver section 56 and demodulator and decoder section 58 of the mobile station to sleep during periods when they are not required to operate, for example during time periods 16 when the mobile station is receiving only MBS data, thereby saving battery power.

In order to provide for macro diversity combining in a mobile station MS of MBS data transmitted from a number of base stations BS, it is necessary for the data in the MBS zone of the downlink frames transmitted by the different base stations to use the same modulation and coding modes is each other and the same organization of the data. In order to achieve this, the MBS server in accordance with this embodiment of the invention includes, as shown in FIG. 9, a MBS manager module 60 which receives the digital content and other messages from preprocessing modules 62 and determines which of the currently available modulation modes should be used for each of the bursts 44 to be transmitted in the MBS zone and what the size and position of each of those bursts should be within the frame memory 24, in order to optimize usage of the available resources.

In order to enable the MBS manager 60 to decide upon the appropriate coding and modulation mode for each burst 44, the MBS server includes a DIUC definition manager 64 which decides, on the basis of appropriate criteria such as the time of day, which subset of the coding and modulation modes should be currently available for use. On the basis of this decision, an MBS-DCD generator 66 constructs the contents of the look-up table 50 and, when these contents change, generates an instruction for incrementing the MBS-DCD count. The MBS manager 60 assembles information including the MBS-MAP message, the MBS-DCD count, the MBS-DCD message and the size, position and modulation and coding mode for each of the bursts 44 and transfers this information to transmitter portion 68. The transmission portion 68 transmits this information to all of the relevant base stations so that each will assemble the MBS zone data in its downlink frames in the same way, to enable mobile stations to perform macro diversity combining of this data.

Although in the embodiment illustrated in FIGS. 5 to 9, the MBS-DCD count and the MBS-DCD message have both been included in the MBS zone, it is within the scope of the invention, as already explained above, for the MBS-DCD count to be omitted, in which case the mobile stations would receive and monitor the MBS-DCD message contained in each frame containing an MBS zone. Further, as already indicated, it would be possible within the scope of the invention for the MBS-DCD message to be omit it from the MBS zone and instead the information which it provides could be included in the DCD message which is provided in the first of the bursts 40 in the segment 16′ of the memory 24, which information would then appear in the traffic periods 16 in the downlink frames. In this case, the DCD count which is included in the downlink map 36 would be repeated in the MBS-MAP message 42.

In view of the foregoing description it will be evident to a person skilled in the art that various modifications may be made within the scope of the invention. While embodiments of the invention have been described in detail, it should be apparent that many modifications and variations thereto are possible within the scope of the invention and are to be construed as being encompassed by the accompanying claims.

Claims

1. A method for providing modulation and coding mode information used for multicast service macro diversity, comprising: sending, by a base station, a message which defines DIUC-relevant information of modulation and coding mode(s) indicated by a downlink interval usage code (DIUC) and used in a multicast and broadcast service (MBS) zone;wherein said message is contained in the MBS zone of a downlink frame.

2. The method according to claim 1, wherein the message is an MBS downlink channel description (MBS-DCD) message.

3. The method according to claim 1, further comprising: sending, by the base station, a MBS-MAP message comprising an information element (IE) indicating an update of the message.

4. The method according to claim 1, further comprising: sending a MBS-MAP message defining a transmitting position of the message.

5. The method according to claim 1, wherein the DIUC-relevant information comprises at least one definition and index of the downlink interval usage code (DIUC).

6. A method for providing modulation and coding mode used by multicast service macro diversity, comprising: sending, by a base station, a downlink channel description (DCD) message defining DIUC-relevant information of a downlink interval usage code (DIUC) used by a downlink burst; andsending, by the base station, a MBS-MAP message in a multicast and broadcast service (MBS) zone comprising an information element (IE) indicating the update of the DCD message.

7. The method according to claim 6, wherein the DIUC-relevant information includes at least one definition and index of the downlink interval usage code (DIUC).

8. A base station, comprising: a transmitter, configured to send a message which defines DIUC-relevant information of modulation and coding mode(s) indicated by a downlink interval usage code (DIUC), and configured to send a multicast and broadcast service map (MBS-MAP) message in a multicast and broadcast service (MBS) zone;the MBS-MAP message comprising an information element (IE) indicating an update of the message.

9. The base station according to claim 8, wherein the message which defines DIUC-relevant information is sent in the MBS zone.

10. The base station according to claim 9, wherein the MBS-MAP message defining a transmitting position of the message which defines DIUC-relevant information.

11. The base station according to claim 9, wherein the message is a MBS downlink channel description (MBS-DCD) message.

12. The base station according to claim 8, wherein the message is a downlink channel description (DCD) message.

13. The base station according to claim 11, wherein the DIUC-relevant information comprises at least one definition and index of the downlink interval usage code (DIUC).

14. The base station according to claim 11, wherein the DIUC-relevant information of modulation and coding mode(s) comprises a list of coding and modulation modes currently available for use in the MBS zone.

15. A mobile station (MS) for receiving multicast and broadcast service (MBS) data, comprising: a receiver, configured to receive a message which defines DIUC-relevant information of modulation and coding mode(s) indicated by a downlink interval usage code (DIUC), and to receive a multicast and broadcast service map (MBS-MAP) message in a multicast and broadcast service (MBS) zone, the MBS-MAP message comprising an information element (IE) indicating the update of the message;the receiver further configured to receive the MBS data according to the DIUC-relevant information of modulation and coding mode(s) contained in the message.

16. The MS according to claim 15, wherein the message defines DIUC-relevant information is received by the receiver in the MBS zone.

17. The MS according to claim 16, wherein the message which defines DIUC-relevant information is an MBS downlink channel description (MBS-DCD) message.

18. The MS according to claim 15, wherein the receiver is configured to determine the position of a MBS-MAP message in the downlink frame; andreceive in the multicast and broadcast service zone of the downlink frame, the MBS-DCD message according to the MBS-MAP message.

19. The MS according to claim 15, wherein the message is a downlink channel description (DCD) message.

20. A mobile station according to claim 15, wherein the DIUC-relevant information comprises at least one definition and index of the downlink interval usage code (DIUC).