HK1176761A - Transmission of mbms in an ofdm communication system - Google Patents

Description

Transmission of MBMS in OFDM communication system

The present application is a divisional application filed on 12/2007 under the name of "transmission of MBMS in OFDM communication" with application number 200780049679.1.

Technical Field

The present invention relates generally to mobile communication systems supporting orthogonal frequency division multiplexing and in particular to mobile communication systems supporting the proposed multimedia broadcast/multicast service.

Background

With the development of communication technology, services provided in mobile communication systems are evolving to include multimedia broadcast communication services capable of supporting multimedia packet services, so as to enable simultaneous transmission of large amounts of bulk data to many User Equipments (UEs). To support multimedia broadcast communications, the third generation partnership project (3GPP) has proposed a multimedia broadcast/multicast service (MBMS) in which one or more multimedia data resources provide services to a plurality of UEs.

The proposed MBMS service may transmit the same multimedia data to a plurality of UEs through a wireless Orthogonal Frequency Division Multiplexing (OFDM) network. The MBMS service will be able to save wireless transmission resources by allowing a plurality of UEs to share one radio channel. The MBMS service is intended to support transmission of multimedia data such as real-time images and voice, still images, and text.

The basic unit of time for transmitting and multiplexing signals, including data, control and reference signals, in an OFDM system is an OFDM symbol, which consists of a Cyclic Prefix (CP) followed by a useful OFDM symbol. A useful OFDM symbol is the sum of a number of sub-carriers, each of which can carry one modulation symbol, referred to as a Resource Element (RE) in the current 3GPP standard. The RE is a basic frequency unit of signal transmission and multiplexing in the OFDM system.

The current 3GPP standard specifies normal and extended CP lengths to be appended to the useful OFDM symbols to avoid multipath interference at the UE. OFDM symbols with normal length CP (OFSN) may be used to transmit signals requiring small or medium coverage in order to minimize CP overhead. OFDM symbols with extended length CP (OFSE) may be used to transmit signals requiring a large coverage area in order to avoid multipath interference at geographically distant UEs.

When an MBMS service is delivered to a Single Frequency Network (SFN) MBMS service delivery area, the same MBMS signal is transmitted synchronously in time from all cells in the MBMS service delivery area using subcarriers of the same frequency. Since MBMS signals have a large coverage area including a plurality of cells, OFSE is generally required for transmitting MBMS signals.

The term "unicast signals" is commonly used by 3GPP to distinguish between cell-specific signals (i.e., signals that generally differ between cells) and "MBMS" signals, which may be the same signal from multiple cells. The CP length typically used for unicast signal transmission in a cell is referred to as the default CP for that cell.

The 3GPP standard defines a transmission unit called slot (slot) having a length of 0.5ms and consisting of 7 OFSNs or 6 OFSEs. A subframe consisting of two slots is currently considered as a minimum scheduling unit for transmitting and multiplexing a unicast signal and an MBMS signal at a physical layer. A slot or subframe may be viewed as a two-dimensional grid (time and frequency) of multiple REs.

The 3GPP standard also assumes that certain types of unicast signals (e.g., L1/L2 control for Uplink (UL) scheduling, ACK for UL packet transmission, measurement reference signals, broadcast channel and paging channel data, synchronization signals, etc.) need to be multiplexed with the MBMS signal in the same subframe. However, it is not clear how this multiplexing is done. The 3GPP standard seems to assume that certain types of unicast REs (e.g. reference signals) and MBMS signals can be multiplexed in the same OFSE. If this is the case, the following may occur: in a cell with normal CP as default CP, the same type of unicast signal can be transmitted in the OFSN or OFSE at any time. Therefore, it is not clear how to let all UEs receiving unicast signals know the dynamic variation of CP length between those OFDM symbols in which only unicast signals are transmitted and those OFDM symbols in which MBMS and unicast signals are multiplexed, to enable the UEs to detect the useful part of OFDM symbols transmitted after normal or extended CP.

It is desirable not to multiplex MBMS signals and unicast signals in the same OFSE. If this is not possible, it is desirable to provide a method that enables the cyclic prefix length to be determined in an OFDM communication system in which the cyclic prefix length may be dynamically varied. It would also be desirable to provide a method of enabling cyclic prefix length determination in an OFDM communication system that ameliorates or overcomes one or more disadvantages or inconveniences of known cyclic prefix length determination methods.

Disclosure of Invention

In view of this, an exemplary aspect of the present invention provides a method of indicating a cyclic prefix to a User Equipment (UE) in an Orthogonal Frequency Division Multiplexing (OFDM) communication system, the cyclic prefix having a dynamically variable length, the method comprising:

transmitting MBMS Control Channel (MCCH) scheduling information in a system information block in an OFDM broadcast channel in an OFDM cell; and

the MCCH scheduling information is utilized to receive the MCCH, wherein the MCCH contains MBMS Transport Channel (MTCH) scheduling information for indicating to the UE which sub-frame carries the MTCH.

Drawings

FIG. 1 is a schematic diagram of an OFDM communication system;

fig. 2 is a diagram illustrating the inclusion of a cyclic prefix in an OFDM symbol transmitted in the OFDM communication system of fig. 1;

fig. 3 is a schematic diagram illustrating a subframe structure for the OFDM communication system in fig. 1;

FIG. 4 is a schematic diagram illustrating the interrelation between various channels for transmitting information in the OFDM communication system of FIG. 1;

FIG. 5 is a diagram illustrating selected functional components in an exemplary transmitter and UE forming part of the OFDM communication system of FIG. 1;

fig. 6 is a timing diagram illustrating the time location of a correlation peak signal during operation of the OFDM communication system of fig. 1;

FIG. 7 is a timing diagram illustrating the time location of correlation peak signals during operation of the OFDM communication system of FIG. 1;

FIG. 8 is a diagram illustrating selected functional components in an exemplary transmitter and UE forming part of the OFDM communication system of FIG. 1;

fig. 9 is a timing diagram illustrating the time location of correlation peak signals during operation of the OFDM communication system of fig. 1;

fig. 10 is a schematic diagram illustrating an alternative subframe structure for the OFDM communication system in fig. 1;

fig. 11 is a timing diagram illustrating the time location of correlation peak signals during operation of the OFDM communication system of fig. 1; and

fig. 12 is a timing diagram illustrating the time location of a correlation peak signal during operation of the OFDM communication system of fig. 1.

Detailed Description

Exemplary embodiments of the present invention will now be described with reference to the accompanying drawings. It will be appreciated that these embodiments are merely exemplary and are not intended to limit the generality of the invention previously described.

Reference is now made to fig. 1, which generally illustrates an OFDM communication network 10 for providing MBMS services. The content provider 12 provides multimedia content to a broadcast multimedia service center (BM-SC) 14. The multimedia content is transmitted to a plurality of Access Gateways (AGWs) 16 and 18 via communication interfaces 20 and 22. The AGWs 16 and 18 form part of an evolved universal terrestrial radio access network (E-UTRAN) 24. The AGWs 16 and 18 distribute multimedia content to E-UTRAN nodes (enbs) 26 to 36, each providing radio transmission for the multimedia content in a different cell. One or more cells defining an area in which the same MBMS service is delivered are referred to as an MBMS service delivery area. The UEs 38 and 40 are capable of receiving MBMS services in an MBMS service delivery area.

Data is transmitted in OFDM communication system 10 within a series of subframes. A portion of a representative subframe 50 is shown in fig. 2. The subframe includes a series of OFDM symbols, where each OFDM symbol includes a CP 52 and a useful portion 54. Each OFDM symbol is a sum of a series of subcarriers, exemplary subcarriers being labeled 56, 58, 60, and 62. Time length T of whole OFDM symbol_SymbolTime length T equal to CP_CPAnd the sum of the time lengths T of the useful OFDM symbols.

A CP is included in each OFDM symbol to maintain orthogonality between subcarriers. The CP is a copy of the last part of the useful part of the OFDM symbol appended to the front part of the symbol during the guard interval. Multipath transmission of OFDM symbols on subcarriers 56 to 62 causes tones (tones) and delayed copies of the tones to arrive at the UE with some delay spread (delay spread). This results in misalignment and loss of orthogonality between tones. The CP allows the tones to be realigned at the UE, thus regaining orthogonality. Since the amount of time dispersion from the channel is less than the duration of the CP, the CP length is chosen to eliminate the inter-signal interference. Although the amount of overhead increases as the CP becomes longer, the CP must be long enough to account for the expected multipath delay spread experienced by the system.

Fig. 3 is a schematic diagram showing a subframe structure currently proposed by the 3GPP standardization group. The first subframe structure 70 includes 14 OFDM symbols transmitted on a plurality of subcarriers. The single data symbol transmitted by each subcarrier during each OFDM symbol is referred to as a Resource Element (RE). The sub-frame structure 70 is intended to carry unicast signals only and includes normal length CPs.

However, a subframe 72 for carrying both unicast signals and MBMS signals multiplexed in the same subframe is also proposed. The subframe structure 72 is transmitted over the same length of time (i.e., 1ms) as the subframe structure 70. However, because MBMS services may be received at UEs from relatively distant cells, each symbol in the subframe structure 72 needs to include a CP of extended length to ensure that the received MBMS signal is not affected by multipath interference. For example, a normal length CP may have a length of 10 data samples in a 1.25MHz bandwidth system, while an extended length CP may have a length of 32 data samples in a 1.25MHz bandwidth system. REs constituting a part of the first three symbols of the subframe structure 72 are defined in the current 3GPP standard to be used only for unicast signals, while REs constituting a part of the remaining nine symbols of the subframe structure 72 are defined to be capable of carrying both unicast and MBMS signals.

However, it is not yet known how to let all UEs receiving unicast signals from a cell for data reception and/or measurement purposes know the possible dynamic variation of CP length of the received sub-frame. This problem occurs, for example, when: when the default CP length in a particular cell is a normal-length CP but the cell also forms part of an MBMS service delivery area, the MBMS service delivery area requires the use of an extended-length CP during the transmission of all symbols carrying MBMS data. The UE currently has no way of knowing whether the CP length of the OFDM symbols in any given subframe is normal or extended.

In order to enable the UE to determine whether the CP transmitted in any given OFDM subframe is of normal or extended length, the MBMS control or scheduling channel (MCCH or MSCH) may be designed such that the UE can read information from the MCCH or MSCH characterising which sub-channel of the MBMS Transport Channel (MTCH) contains MBMS data (and thus uses an extended length CP).

As can be seen in fig. 4, a special System Information Block (SIB)80 may be included in a conventional OFDM cell-specific Broadcast Channel (BCH) to indicate to the UE the location of the following information transmitted in the MBMS control (signaling) channel (MCCH) 82: this information identifies which subframe will carry the MTCH and thus identifies the length of the CP used in the subframe in the MBMS service delivery area. Exemplary sub-frames 84 to 94 are shown in fig. 4. Subframes 84, 88, and 90 include unicast symbols only and thus use normal length CP, while subframes 86, 92, and 94 multiplex both MBMS symbols and unicast symbols and use extended length CP.

Advantageously, no additional complexity is required for the UE physical layer processing in this case, although the UE must be able to receive not only the OFDM cell-specific BCH but also the MBMS mscch, regardless of whether the particular UE wishes to receive the MBMS service.

An alternative to the above technique is illustrated in fig. 10. The figure shows a first new sub-frame structure 160 and a second new sub-frame structure 180 used when MBMS signals and unicast signals are multiplexed in the same sub-frame and transmitted from a cell having normal-length and extended-length CPs as default CPs, respectively. In the new sub-frame 160, the first n (typically 2 or 3) OFDM symbols 162 always use normal-length CP for unicast signal transmission only (i.e., primarily L1/L2 control for UL, RS and ACK), and the remaining OFDM symbols 164 use extended-length CP for primary MBMS signal transmission.

In the new sub-frame 180, the first n (typically 2 or 3) OFDM symbols 182 always use extended length CP to transmit unicast signals only (i.e., primarily L1/L2 control for UL, RS and ACK), and the remaining OFDM symbols 184 use extended length CP to primarily transmit MBMS signals.

The new subframes 160 and 180 should be such that the number of OFDM symbols used for MBMS must be the same and each of these symbols must end at the same time.

Advantageously, this new subframe structure 160 enables the UE to receive the L1/L2 control transmitted in the first n OFDM symbols in the subframe without knowing whether the MBMS signal is transmitted in the subframe or not, since the first n OFDM symbols always use a normal-length CP. In addition, if the UE uses only the RS in the first OFDM symbol in one slot (two slots in one subframe) for measurement, the UE does not need to know whether the MBMS is transmitted in the subframe or not. If the subframe carrying the BCH always uses the default CP length, the UE does not need to know whether MBMS is transmitted in the subframe or not.

As another alternative to the above technique, or in addition to the above technique, when the UE misses or cannot read the MCCH and the UE still needs to know the CP length used in all OFDM symbols of the subframe, the UE may perform blind detection of the CP length. This substitution is only needed when the UE receives a unicast signal from a cell having a normal-length CP as a default. Fig. 5 is a schematic diagram illustrating selected functional blocks in a transmitter 100 and a receiver (UE)102 in which CP length blind detection is performed. After modulation and time/frequency mapping in block 104, an Inverse Fast Fourier Transform (IFFT) is performed in the transmitter at IFFT block 106 to transform the frequency domain data into a time domain signal. CP insertion block 108 is then used to introduce a cyclic prefix into the OFDM symbol to avoid inter-symbol interference at the UE, and RF block 110 is then used to transmit the signal over channel 112.

At the UE102, a corresponding RF block 114 is used to receive and digitize the signal transmitted over the channel 112. The CP length detection block 116 then detects the length of the CP used in a given OFDM subframe. Thereafter, the CP is removed by CP removal block 118, and the useful part of the OFDM symbol is transformed from the time domain to the frequency domain by FFT block 120, before time/frequency demapping and demodulation by processing block 122.

UE102 cross-correlates the received signal output from RF block 114 using a copy of the Reference Signal (RS) transmitted during the first symbol in the OFDM subframe. The replica RS is stored in the memory 124 and output through IFFT block 126, IFFT block 126 being functionally identical to IFFT block 106 in transmitter 100. The output of the IFFT block 126 is correlated (correct) with the output of the RF block 114 by a correlator 128 and the length of the CP is detected by a CP detection block 130.

Fig. 6 shows selected data samples in an exemplary first OFDM symbol in subframe 140, as well as a first theoretical correlation peak P1 occurring at the beginning of the useful portion of an OFDM symbol using normal length CP and a second theoretical correlation peak P2 occurring at the beginning of the useful portion of an OFDM symbol using extended length CP. If the UE102 can always correctly estimate the time position of the start of each symbol, T _ ref, then the UE102 need only compare the two correlation values P1 and P2 to decide which CP length to use.

There is always an error in estimating the time position T _ ref of the start of each symbol, so the UE102 needs two windows W1 and W2 in which to search for a correlation signal peak. The maximum window size MW is given by the time position difference between the peaks P1 and P2, which can be seen as the maximum error tolerance for the estimation of the time position T _ ref of the start of each subframe.

However, since the time interval between RS transmissions is typically 6 subcarriers, an additional correlation peak occurs in the profile (profile) shown in fig. 6. Also shown in this figure is a first extra correlation peak EP1 due to the use of normal length CP and a second extra correlation peak EP2 due to the use of extended length CP. As can be seen in table 1, depending on the bandwidth of the OFDM communication system, the correlation peak EP2 may be spaced from the correlation peak P1 (and the correlation peak EP1 may be spaced from the correlation peak P2) by only one sample. This leaves a very small practical window for considering the T _ ref estimation error.

TABLE 1

(assume T _ ref is 0)

System (MHz)	1.25	2.5	5	10	15	20
							P1 (sampling position)	10	20	40	80	120	160
P2 (sampling position)	32	64	128	256	384	512
							MW (P2-P1) (number of samples)	22	44	88	176	264	352
EP2 (sampling position)	11	22	43	86	128	171
							PW (EP2-P1) (number of samples)	1	2	3	6	8	11

A first way to solve this problem is to use different RS sequences (labeled RS1 and RS2 in fig. 5) in the first OFDM symbol in the subframe where MBMS signals can be transmitted and MBMS signals cannot be transmitted. As seen in fig. 7, the UE102 performs cross-correlation of the received signal with each copy of RS1 and RS2 to generate two profiles. The CP length may then be determined from the profile with the stronger correlation peak of the two profiles.

A second way to solve this problem is to increase the distance between the correlation peaks P1 and EP2 (and between EP1 and P2). One way to achieve this separation is by applying a predetermined non-zero Cyclic Delay (CD) to OFDM symbols in subframes where MBMS signals can be transmitted and zero CD to OFDM symbols in subframes where MBMS signals cannot be transmitted. Fig. 8 is a schematic diagram showing selected functional blocks in a transmitter 150 and a receiver (UE)152, which transmitter 150 and receiver (UE)152 are functionally identical to transmitter 100 and receiver (UE)102 shown in fig. 5, except that a CD insertion block 154 is added in transmitter 150 between IFFT block 106 and CP insertion block 108, and only a single RS sequence corresponding to a zero CD RS sequence is stored in storage block 124 of UE 152.

In operation, the UE152 performs one correlation with a zero CD RS sequence to generate a single correlation peak profile and then determines the CP length based on which window (i.e., either window W1 centered at the start of the useful part of the OFDM symbol when normal-length CP is used or window W2 centered around the CD samples starting from the center of W1) has the strongest correlation peak.

As can be seen in fig. 9, the result of applying a predetermined non-zero CD to OFDM symbols in a subframe in which an MBMS signal is transmitted and applying a zero CD to OFDM symbols in a subframe in which an MBMS signal is not transmitted causes separation of correlation peaks P1 and EP 2. In principle, in a subframe in which an MBMS signal is transmitted, only the non-zero CD needs to be applied to the RS in the first OFDM symbol. However, to simplify system implementation and to make the CD more transparent to the UE, it may be desirable to apply a non-zero CD for all OFDM symbols in a given subframe.

Table 2 below shows an example of using a non-zero CD. It can be seen that the actual window PW is much larger than in table 1.

TABLE 2

System, MHz	1.25	2.5	5	10	15	20
							P1	10	20	40	80	120	160
CD	8	17	35	71	107	143
							EP2	19	39	78	157	235	314
PW＝(EP2-P1)	9	19	38	77	115	154

Another alternative to the above technique is provided by combining the blind CP length detection described in connection with fig. 5 to 9 with the new subframe structure 160 shown in fig. 10. In this alternative embodiment, a new subframe structure 160 is used for transmitting the MBMS signal.

There are two variations of this alternative embodiment. In a first of these variants, two different RS sequences are used in the first OFDM symbol in a subframe where only unicast signals or unicast or MBMS signals are transmitted. In operation, the UE receives unicast signals in the first n OFDM symbols with knowledge of the normal length CP used. During the first OFDM symbol, the UE detects which of the RS sequences is used, as shown in fig. 11. The UE then uses the detected RS to decode other unicast data channels, such as the L1/L2 control channel.

In a second variant, the same RS sequence is used in the first OFDM symbol in a subframe in which only unicast or MBMS signals are transmitted. In a subframe where MBMS is transmitted, the CD will be set to a non-zero value during the first n OFDM symbols. In operation, the UE receives unicast signals in the first n OFDM symbols with knowledge of the normal length CP used. The UE may decode other unicast data channels such as the L1/L2 control channel without any delay. During the first OFDM symbol, the UE detects whether a zero CD or a non-zero CD has been applied to the RS, as shown in fig. 12.

In principle, in a subframe in which an MBMS signal is transmitted, only the non-zero CD needs to be applied to the RS in the first OFDM symbol. However, to simplify system implementation and to make the cyclic delay transparent to the UEs receiving the L1/L2 control channel, it may be desirable to apply a non-zero CD to the first n OFDM symbols in the subframe.

Both variants advantageously enable the UE to receive the L1/L2 control transmitted in the first n OFDM symbols of a subframe without knowing whether an MBMS signal is transmitted in the subframe or not. In addition, the UE may detect the CP length used in the (n + 1) th, n +2 … th OFDM symbol. CP length detection at the UE does not involve an increase in L1/L2 control channel decoding delay, or involves a minimal increase in L1/L2 control channel decoding delay.

It will be appreciated that modifications or additions may be made to the embodiments described above without departing from the spirit or ambit of the present invention as defined in the appended claims.

Another exemplary aspect of the present invention provides a method of identifying a cyclic prefix length in an OFDM communication system, the cyclic prefix having a dynamically variable length, the method including:

correlating the stored copies of the one or more reference signals capable of being transmitted in the kth OFDM symbol in the subframe with the received signal to generate one or more correlation profiles;

the kth may be the first OFDM symbol in the subframe

In case only one relevant profile is generated, the method further comprises the steps of:

detecting a correlation signal peak proximate in time to a first possible start of a useful portion of a hypothetical OFDM symbol assumed to include a normal-length cyclic prefix and a second possible start of a useful portion of a hypothetical OFDM symbol assumed to include an extended-length cyclic prefix; and

the length of the cyclic prefix is determined from the strength of the detected correlation peak.

In one exemplary embodiment, a first reference signal is transmitted in a subframe carrying an MBMS signal and a second reference signal is transmitted in a subframe not carrying an MBMS signal, the first and second reference signals being different from each other, the method further comprising the steps of:

correlating the stored copies of the first and second reference signals with the received signal, respectively, to produce first and second correlation profiles, respectively; and

the cyclic prefix length is determined from the profile of the first and second profiles that causes the strongest correlation peak.

In another exemplary embodiment, the method further comprises:

the OFDM symbols are processed prior to transmission to introduce a separation between the two possible correlation signal peaks.

The separation may be introduced by applying a non-zero cyclic delay to OFDM symbols in the subframe that use an extended-length cyclic prefix and by applying a zero cyclic delay to OFDM symbols in the subframe that do not use an extended-length cyclic prefix.

Another exemplary aspect of the present invention provides a method of identifying a cyclic prefix having a dynamically variable length in an OFDM communication system, the method including:

in an OFDM cell, transmitting MCCH scheduling information in a system information block in an OFDM broadcast channel; and (c) and (d).

Receiving an MCCH using the MCCH scheduling information, wherein the MCCH contains MTCH scheduling information for indicating to the UE which sub-frame carries MTCH; and is

Correlating a stored copy of one or more reference signals capable of being transmitted in an OFDM symbol with a received signal in the event that an MBMS point-to-multipoint (point-to-multipoint) control channel is missed or cannot be read;

detecting a correlation signal peak proximate in time to a first possible start of a useful portion of a hypothetical OFDM symbol assumed to include a normal-length cyclic prefix and a second possible start of a useful portion of a hypothetical OFDM symbol assumed to include an extended-length cyclic prefix; and

determining the length of the cyclic prefix according to the strength of the detected correlation peak.

Another exemplary aspect of the present invention provides a method of OFDM data transmission in a subframe consisting of m OFDM symbols, wherein a cyclic prefix length of each symbol can be dynamically changed, the method comprising the steps of:

a normal-length cyclic prefix is included in the first n OFDM symbols in the subframe, n being an integer having a value less than m, and an extended-length cyclic prefix is included in the remaining m-n OFDM symbols in which the MBMS signal is transmitted.

The value of n may be 3 or less.

Another exemplary aspect of the present invention provides a cyclic prefix length detection method in which data is transmitted as described above, the cyclic prefix length detection method including the steps of:

correlating the stored copies of the one or more reference signals capable of being transmitted in the kth OFDM symbol transmitted in the subframe with the received signal.

The kth symbol may be the first OFDM symbol in a subframe

In one exemplary embodiment, a first reference signal is transmitted in a subframe carrying an MBMS signal and a second reference signal is transmitted in a subframe not carrying an MBMS signal, the first and second reference signals being different from each other, the method further comprising the steps of:

correlating the stored copies of the first and second reference signals with the received reference signals, respectively, to generate first and second correlation profiles, respectively; and

the length of the cyclic prefix used in the remaining m-n symbols is determined from the profile of the first and second profiles that gives rise to the strongest correlation peak.

In another exemplary embodiment, the method further comprises the steps of:

the first OFDM symbol is processed prior to transmission to introduce a separation between the two possible correlation signal peaks.

The separation may be introduced by applying a non-zero cyclic delay to each of the first n OFDM symbols in the subframe that use an extended-length cyclic prefix and by applying a zero cyclic delay to each of the first n OFDM symbols in the subframe that do not use an extended-length cyclic prefix.

This application is based on and claims priority from australian patent application No. 2007900103 filed on 10/1/2007, the contents of which are incorporated herein by reference in their entirety.

Claims (26)

1. A method implemented in a base station for Orthogonal Frequency Division Multiplexing (OFDM) data transmission in a subframe consisting of m OFDM symbols, comprising:

transmitting a default cyclic prefix for each of a first one or more OFDM symbols in the subframe, the number of the first one or more OFDM symbols being an integer n having a value less than m; and

an extended length cyclic prefix is transmitted for the remaining m-n OFDM symbols,

wherein a Multimedia Broadcast Multicast Service (MBMS) signal is transmitted in the remaining m-n OFDM symbols.

2. The method of claim 1, wherein the default cyclic prefix comprises a normal-length cyclic prefix or an extended-length cyclic prefix.

3. The method of claim 1, wherein the default cyclic prefix comprises a cyclic prefix for unicast signal transmission.

4. The method of claim 1, wherein n is equal to or less than 3.

5. The method of claim 1, wherein n is 2 or 3.

6. The method of claim 1, wherein a cyclic prefix length of each OFDM symbol varies dynamically.

7. A method implemented in a user equipment for Orthogonal Frequency Division Multiplexing (OFDM) data reception in a subframe consisting of m OFDM symbols, comprising:

receiving a default cyclic prefix for each of a first one or more OFDM symbols in the subframe, the number of the first one or more OFDM symbols being an integer n having a value less than m,

wherein the sub-frame includes an extended length cyclic prefix of the remaining m-n OFDM symbols, and

wherein a Multimedia Broadcast Multicast Service (MBMS) signal is transmitted in the remaining m-n OFDM symbols.

8. The method of claim 7, wherein the default cyclic prefix comprises a normal-length cyclic prefix or an extended-length cyclic prefix.

9. The method of claim 7, wherein the default cyclic prefix comprises a cyclic prefix for unicast signal transmission.

10. The method of claim 7, wherein n is equal to or less than 3.

11. The method of claim 7, wherein n is 2 or 3.

12. The method of claim 7, wherein a cyclic prefix length of each OFDM symbol varies dynamically.

13. A base station for Orthogonal Frequency Division Multiplexing (OFDM) data transmission in a subframe consisting of m OFDM symbols, comprising:

a transmitter to transmit a non-multimedia broadcast multicast service (non-MBMS) signal in a first one or more OFDM symbols in the subframe, the first one or more OFDM symbols being a number n of integer values less than m, and the transmitter to transmit the MBMS signal in the remaining m-n OFDM symbols,

wherein a default cyclic prefix is transmitted for the non-MBMS signal and an extended length cyclic prefix is transmitted for the MBMS signal.

14. The base station of claim 13, wherein the default cyclic prefix comprises a normal-length cyclic prefix or an extended-length cyclic prefix.

15. The base station of claim 13, wherein the default cyclic prefix comprises a cyclic prefix for unicast signal transmission.

16. The base station of claim 13, wherein n is equal to or less than 3.

17. The base station of claim 13, wherein n is 2 or 3.

18. The base station of claim 13, wherein a cyclic prefix length of each OFDM symbol varies dynamically.

19. The base station of claim 13, wherein the non-MBMS signal comprises a unicast signal.

20. A user equipment for Orthogonal Frequency Division Multiplexing (OFDM) data reception in a subframe consisting of m OFDM symbols, comprising:

a receiver to receive a non-multimedia broadcast multicast service (non-MBMS) signal in a first one or more OFDM symbols in the subframe, the number of the first one or more OFDM symbols being an integer n having a value less than m,

wherein the MBMS signal is transmitted in the remaining m-n OFDM symbols,

wherein a default cyclic prefix is transmitted for the non-MBMS signal and an extended length cyclic prefix is transmitted for the MBMS signal.

21. The user equipment of claim 20, wherein the default cyclic prefix comprises a normal-length cyclic prefix or an extended-length cyclic prefix.

22. The user equipment of claim 20, wherein the default cyclic prefix comprises a cyclic prefix for unicast signal transmission.

23. The user equipment of claim 20, wherein n is equal to or less than 3.

24. The user equipment of claim 20, wherein n is 2 or 3.

25. The user equipment of claim 20, wherein a cyclic prefix length of each OFDM symbol varies dynamically.

26. The user equipment of claim 20, wherein the non-MBMS signal comprises a unicast signal.