RU2364045C2 - Increasing pilot carrier activation for channel and interference assessment - Google Patents

Abstract

FIELD: communication facilities.

SUBSTANCE: invention concerns systems, devices and methods of dynamic resource assignment for selective boost of channel assessment property of a receiver in multiple access system with orthogonal frequency distribution (OFDMA). Wireless communication system can use configuration of common pilot channel in channel assessment at one or more receivers establishing communication with the system. Receiver establishing communication with the system can be unable to demodulate received data due to incorrect channel assessment. Receiver can send request for additional channel assessment resources to a system transmitter. Wireless communication system can provide additional resources of channel assessment by inclusion of dedicated pilot channels to one or more frequencies selected for the receiver symbols. If the receiver still cannot demodulate received data, wireless communication system can include additional increasing pilot channels to the receiver symbol.

EFFECT: enhanced reception accuracy.

44 cl, 8 dwg

Description

BACKGROUND OF THE INVENTION

This application claims priority based on provisional US patent application No. 60/588686 entitled "Incremental Pilot Insertion For Channel / Interference Estimation", filed July 16, 2004, and US patent application No. 60/638536, filed December 22, 2004, which are hereby incorporated by reference in full.

FIELD OF THE INVENTION

The disclosure generally relates to the field of wireless communications. In particular, the disclosure relates to the allocation of resources for channel estimation.

Description of the prior art

In a wireless communication system, for example, implementing orthogonal code division multiple access (OFDMA), the receiver may be able to perform channel estimation in the order of the demodulation process. The receiver may perform channel estimation in the OFDMA system to compensate for time-dependent frequency selective attenuation.

A receiver in an OFDMA system can estimate the channel blindly, not knowing anything about the transmitted data, or can estimate the channel partially based on one or more pilot channels, which are broadcast and known to the receiver. In a configuration that uses pilot channels to assist the receiver in channel estimation, a trade-off is achieved between the resources allocated for channel estimation and system performance.

The communication system allocates a minimum number of pilot signals for channel estimation to maximize the available signal bandwidth. However, insufficient allocation of resources for channel estimation can lead to an incorrect channel estimate, which can lead to an inability to demodulate received data and to a decrease in system performance.

On the contrary, the allocation of excess resources for channel estimation allows us to ensure that each receiver is able to determine the correct channel estimate, but can overload the system and reduce its throughput. In this configuration, the system ensures that the weakest receiver is able to determine the correct channel estimate due to the bandwidth of other, better located receivers.

It is desirable to allocate resources in a wireless communication system in such a way as to provide an accurate estimate of the channel at the receivers, but to minimize the allocation of resources so as not to reduce the channel throughput without need.

SUMMARY OF THE INVENTION

Disclosed are systems, apparatus, and methods for dynamically allocating resources to selectively increase a receiver's ability to determine a channel estimate in an orthogonal frequency division multiple access (OFDMA) system. A wireless communication system may use a common pilot channel configuration to aid in channel estimation at one or more receivers in communication with the system. A receiver communicating with the system may not be able to demodulate received data due to an inaccurate channel estimate. The receiver may transmit to the transmitter in the system a request for additional channel estimation resources. A wireless communication system may provide additional channel estimation resources by including dedicated pilot channels in one or more frequencies allocated to symbols for the receiver. If the receiver is still unable to demodulate the received data, the wireless communication system may include additional pilot channels in increasing order in the symbol associated with the receiver.

The disclosure includes a device for dynamically allocating resources for channel estimation. The device includes a channel quality module capable of determining a request for channel estimation resources, and a resource allocation module connected to a receiver and capable of determining a main resource level and a variable resource level, wherein the variable resource level is based at least in part on a channel estimate resource request . An embodiment may also include a transmitter capable of transmitting a signal, a portion of which is dedicated to channel estimation based on a main resource level and a variable resource level.

The disclosure also includes an apparatus for dynamically allocating resources for channel estimation, including a common pilot module capable of determining a first subset of carriers from a set of orthogonal code division multiple access (OFDMA) carriers, wherein the first subset of carriers is allocated to the common pilot , a symbol module capable of determining a second subset of OFDMA carriers allocated to a communication channel, wherein the second subset of OFDMA carriers is different from the first subset of OFDMA carriers, a dedicated pilot module a capable of extracting at least one carrier from a second subset of OFDMA carriers for channel estimation, a symbol generator capable of generating an OFDMA symbol from OFDMA carriers, and a transmitter capable of transmitting an OFDMA symbol having dedicated pilot allocated for channel estimation.

The disclosure also includes a device for channel estimation based on dynamic resource allocation, including a receiver capable of receiving an orthogonal frequency division multiple access (OFDMA) symbol having resources allocated for channel estimation, a conversion module connected to the receiver and capable of converting OFDMA symbol in the aggregate of carriers, a carrier allocation module capable of determining a first subset of carriers corresponding to the common pilot signal, a second subset of carriers corresponding to a carrier for transmitting data, and at least one carrier from the second subset of carriers corresponding to the dedicated pilot signal, a channel estimator connected to the transform module and the carrier allocation module and capable of determining the channel estimate partially based on the common pilot signal and the allocated a pilot signal, and a demodulator capable of demodulating carriers for data transmission in part based on a channel estimate.

The disclosure also includes a method for generating a signal having dynamically allocated channel estimation resources, including the steps of: assigning a main level of channel estimation resources, determining a request for additional resources, allocating additional resources for channel estimation, and generating a signal partially based on the main resource level and additional resources.

The disclosure also includes a method of receiving a signal having dynamically allocated channel estimation resources, including the steps of receiving an orthogonal frequency division multiple access (OFDMA) symbol, determining a basic level of resources for channel estimation included in an OFDMA symbol, additional channel estimation resources included in the OFDMA symbol determine the channel estimate based on the base layer and additional channel estimation resources and demodulate the received symbol partially based on the estimate channel.

Brief Description of the Drawings

Signs, objectives, and advantages of embodiments of the disclosure will be apparent from the following detailed description, taken in conjunction with the drawings provided with an end-to-end notation.

Figure 1 - functional block diagram of an embodiment of a wireless communication system that implements the dynamic inclusion of a pilot signal for channel estimation.

2A-2B are functional block diagrams of embodiments of a generator and a receiver capable of dynamically turning on a pilot signal for channel estimation.

Figure 3 is a diagram illustrating an example spectrum of an OFDMA system for various common and dedicated pilot channel configurations.

4A-4B are logical flowcharts of embodiments of processes for dynamically allocating channel estimation resources by turning on a pilot signal.

5 is a flowchart of an embodiment of a process for allocating channel estimation resources by turning on a pilot signal.

6 is a functional block diagram of an embodiment of a data receiving process in a system having a dynamic allocation of channel estimation resources.

DETAILED DESCRIPTION OF THE INVENTION

A wireless communication system, such as an OFDMA communication system, can allocate a basic resource level for channel estimation and receiver interference. The basic level of resources can be determined based on the nominal operating parameters of the receivers and the corresponding probability of successful demodulation of data, given the basic level of resources and operating parameters of the receiver.

However, due to the variable nature of operating conditions and channel characteristics for a portable user terminal in a wireless communication system, there are conditions where the basic level of resources is insufficient so that the receiver can accurately estimate the channel and interference. An inaccurate channel estimate and interference can result in the receiver being unable to demodulate data using the estimate. The receiver may indicate or otherwise inform the transmitter of unsuccessful data demodulation. For example, the receiver may be able to send a retransmission request, or it may be able to cancel sending an acknowledgment message in case of unsuccessful data demodulation.

The wireless communication system may then allocate additional resources for channel estimation and interference. According to one embodiment, a wireless communication system may allocate additional resources that increase the ability of a plurality of receivers to estimate channel and interference. According to another embodiment, a wireless communication system may allocate additional resources for channel estimation and interference for a specific receiver reporting inability to demodulate data. A wireless communication system may continue to dynamically allocate channel estimation resources and interference to each receiver.

An exemplary OFDMA wireless communications system capable of dynamically allocating resources includes a transmitter capable of providing one or more pilot signals for channel estimation. The main resource level may correspond to the configuration of the common pilot signal, which may be organized, for example, in the form of a substantially comb configuration. In addition, the comb configuration of the common pilot signal can take place at different frequencies at different times, and the pattern occupied by the pilot signals can be predetermined. In one example, the pilot signals may be able to act as a step comb, with the pilot signals alternating between two sets of frequencies. A wireless communication system may transmit pilot signals during data symbol transmission to receivers, or may be capable of transmitting pilot signals during predetermined time intervals for exchanging control information. According to another embodiment, the main resource level may correspond to one or more dedicated pilots or combinations of common pilots in combination with one or more dedicated pilots.

Each active receiver in an OFDMA wireless communication system may be assigned a subset of OFDM frequencies. Each receiver may be able to have configuration information for the common pilot and may be able to determine the channel estimate and interference based on the received common pilots. The receiver can then demodulate the received data in part based on the channel estimate and interference. The receiver can demodulate the received data provided that the channel and interference estimates are sufficient, the received data is not damaged, and the received signal strength is sufficient.

In some cases, the receiver may not be able to determine a sufficiently accurate channel and interference estimate based on common pilot signals. Inaccurate channel estimation and interference may result in the receiver being unable to demodulate received data. In such a situation, the receiver may not transmit an acknowledgment message (ACK), may transmit a retransmission request, or may otherwise indicate an inability to decode the received data.

The transmitter in the wireless communication system may then retransmit unsuccessfully received data. A wireless communication system may also be able to increase the amount of resources available to the receiver for channel estimation and interference. For example, a wireless communication system may be able to include additional pilot signals. According to one embodiment, the wireless communication system includes additional dedicated pilot signals. Dedicated pilots may be included in the OFDMA symbol instead of one or more frequencies that are typically modulated by data. Thus, the extracted pilot signal is actually coded perforated per data symbol. The dedicated pilot does not affect the channel bandwidth of any other user, since the dedicated pilot does not use the resources of other receivers. The receiver can use the dedicated pilot signal, coded perforated on the transmitted data, to further refine the channel estimate and interference. The receiver can determine the position and number of allocated pilot signals based on a predetermined algorithm. According to another embodiment, the wireless communication system transmits the position and number of allocated pilot signals to the receiver via a control or overhead channel.

According to one embodiment, other receivers may continue to estimate the channel and interference, unaware of the allocated pilot signals. According to another embodiment, one or more other receivers may use the dedicated pilot information to further improve the accuracy of the channel estimate and the interference determined by these receivers. Thus, the wireless communication system dynamically changes the amount of resources allocated for channel estimation and interference.

1 is a functional block diagram of an embodiment of a wireless communication system 100 having a dynamic pilot enable for channel estimation. The system includes one or more fixed elements that can communicate with user terminal 110. User terminal 110 may be, for example, a cordless telephone capable of operating according to one or more communication standards. The user terminal 110 may be a portable device, a mobile device, or a stationary device. The user terminal 110 may also be called a mobile device, a mobile terminal, a mobile station, user equipment, a mobile phone, a handset, and the like. Although only one user terminal 110 is shown in FIG. 1, it should be understood that a conventional wireless communication system 100 is capable of communicating with multiple user terminals 110.

User terminal 110 typically communicates with one or more base stations 120a or 120b, denoted herein as sectorized masts of cellular communications. User terminal 110 typically communicates with a base station, for example 120b, which provides the highest signal strength at the receiver of user terminal 110.

Each of the base stations 120a and 120b may be connected to a base station controller (BSC) 140, which routes communication signals to and from respective base stations 120a and 120b. BSC 140 is connected to a mobile switching center (MSC) 150, which may be able to act as an interface between a user terminal 110 and a public switched telephone network (PSTN) 150. MSC can also be able to act as an interface between a user terminal 110 and a network 160 The network 160 may be, for example, a local area network (LAN) or wide area network (WAN). According to one embodiment, the network 160 includes the Internet. Therefore, MSC 150 is connected to the PSTN 150 and network 160. MSC 150 may also be able to coordinate inter-system handoffs with other communication systems (not shown).

The wireless communication system 100 may be configured as an OFDMA system communicating in a forward link and a reverse link in an OFDM communication mode. The term “forward link” means a communication link from base stations 120a or 120b to a user terminal 110, and the term “reverse link” means a communication link from a user terminal 110 to base stations 120a or 120b. Both base stations 120a and 120b and user terminal 110 may allocate resources for channel estimation and interference. For example, both base stations 120a and 120b and user terminal 110 may transmit broadcast pilots that are used by respective receivers to estimate channel and interference. For simplicity, when describing an embodiment of the system, resource allocation for channel estimation and interference on the forward link is considered. However, it is understood that such resource allocation is not limited to application to the forward link, but can be used both on the forward link and the reverse link, or can be implemented on only one link.

Base stations 120a and 120b may be able to broadcast a common pilot signal as the primary resource level allocated for channel and interference estimation. A common pilot may include a number of frequencies selected from a set of OFDM frequencies. For example, a common pilot signal may be generated from equidistant frequencies selected from a set of OFDM frequencies. The equidistant configuration may be called a comb pilot. As described above, in other embodiments, a core resource level may be allocated to dedicated pilots or combinations of common pilots with dedicated pilots.

A common pilot signal may include two or more sets of frequencies selected from a set of OFDM frequencies and may transmit one of the sets of frequencies based on a predetermined sequence or algorithm. According to one embodiment, the common pilot may be one of two sets of frequencies, and a base station, for example 120a, may switch between two sets of frequencies.

The common pilot and modulated data experience distortion and degradation, due in part to the channel. User terminal 110 may receive a common pilot along with modulated data from a base station, for example 120a. The time-domain signal received by the user terminal can be expressed as y (t) = s (t) * h (t) + i (t) + n (t), where s (t), h (t), i (t ) and n (t) express modulated data, channel, interference, and additive noise, respectively. The symbol "*" indicates a convolution operator.

The user terminal 110 may determine the channel estimate and interference based on common pilots, and may determine the estimate in the frequency domain, although the estimate in the time domain can be determined instead of, or in conjunction with the estimate in the frequency domain. The user terminal 110 may then demodulate the received signal to recover data.

The user terminal 110 may not be able to successfully demodulate the received signals because the channel quality is insufficient and cannot support the data rate. Alternatively, the user terminal 110 may not be able to successfully demodulate received signals even on a channel that supports a data rate, since the degradation due to an incorrect channel estimate and interference is large enough to cause a decoding error.

In the first case, the allocation of additional resources for channel estimation and interference does not increase insufficient channel quality. In this situation, the transmitter may need to reduce the data rate. However, the allocation of additional resources for channel estimation and interference in the latter case may allow the user terminal 110 to demodulate data at the current data rate.

The user terminal 110 may be able to indicate to the wireless communication system 100, for example through the base station 120a, about the inability to demodulate data. The indication may take the form of a message or its absence transmitted from the user terminal 110 to the base station 120a. The user terminal 110 may transmit an indication, for example, on a control channel or a feedback channel.

In one embodiment, the indication may be a retransmission request; in another embodiment, the indication may be the absence of an acknowledgment message (ACK).

If the wireless communication system 100 determines the inability of the user terminal 110 to demodulate data, for example, by receiving an indication from the base station 120a, the wireless communication system 100 may allocate additional resources for channel estimation and interference. According to one embodiment, base station 120a includes additional frequencies in common pilot signals. According to another embodiment, the base station may include dedicated pilot signals that code-punch data transmitted to user terminal 110, which indicates an inability to demodulate data. Base station 120a may also be able to reduce the data rate for data transmitted to user terminal 110.

The dedicated pilot signals are selected from the frequencies used to generate the OFDMA symbol transmitted to the user terminal 110. Since the pilot carrier is selected from one of the data carriers, the advantage of the dedicated pilot is that it experiences the same channel fluctuations and interference that data is experiencing. However, since the carrier for the dedicated pilot is selected from one of the carriers for data transmission, the allocation of one or more dedicated pilots may result in some loss of data throughput.

The inclusion of dedicated pilot signals in data carriers allows the pilot signals to be in the same channel and interference conditions as the data symbols. The dedicated pilot may be especially useful with the user terminal 110 in determining channel estimates and interference in an adjustable power configuration, where the carrier power on the carriers for transmitting data is much higher than the power on the frequencies of the common pilot signal. Dedicated pilots are also very useful for channel estimation and interference to user terminal 110 when interference or channel fluctuations experienced by data carriers are different from those experienced by frequencies used by common pilots.

According to one embodiment, the dedicated pilot may be an unmodulated harmonic selected from frequencies used to generate the OFDMA symbol transmitted to user terminal 110. According to another embodiment, the dedicated pilot may be empty pilots in which there is no signal not transmitted on a carrier frequency selected from frequencies used to generate the OFDMA symbol transmitted to user terminal 110.

The performance degradation due to the allocation of resources to one or more dedicated pilot signals can be mitigated to some extent by using a hybrid automatic retransmission request (HARQ) configuration, where subsequent data transmissions are carried out at corresponding reduced speeds if the previous transmission was not successfully decoded at the receiver .

Since the dedicated pilot signals are included in the carrier position for data transmission, the allocation of the dedicated pilot signals can be considered as code perforation. The initial data transfer may be particularly sensitive to code punching, since it can occur at the highest coding rate used in the system. According to an embodiment, where the wireless communication system 100 is capable of increasing the dedicated pilot, the additional channel estimation resources and interference are added in retransmissions. If the failure to decode the previous transmission is due to insufficient channel and interference estimation, additional resources will assist the receiver in decoding the retransmitted data. In addition, if the retransmitted data is transmitted at a lower speed than the previous data transmission, the perforation loss can be small. The performance loss due to the inclusion of dedicated pilot signals in subsequent transmissions is less than the performance loss due to the inclusion of dedicated pilot signals in the initial transmission. Therefore, in subsequent transmissions, you can add, accordingly, more assessment resources without creating a significant loss in productivity.

Although the above description of the system 100 of FIG. 1 relates generally to a wireless telephone system, the system 100 is not limited to being implemented as a wireless telephone system, and the system 100 is not limited to having the specific elements shown in FIG. 1. For example, according to another embodiment, each of the base stations 120a and 120b may be referred to as a node B. According to another embodiment, a packet data service node (PDSN) may be implemented in the system 100 instead of or in conjunction with the PSTN 150. The PDSN may act as a network interface packet-switched with the wireless part of the system 100.

Other embodiments of the system 100 may include access points, nodes B, or other structures instead of base stations 120a and 120b. In such an embodiment, systems 100, BSC 130, and MSC 140 may be eliminated and replaced with one or more switches, hubs, or routers.

FIG. 2A is a functional block diagram of an embodiment of a generator 200 capable of dynamically allocating resources for channel and interference estimation. An embodiment of the generator 200 may be implemented, for example, at one or both of the base stations 120a or 120b and the user terminal 110 shown in the wireless communication system 100 of FIG. 1.

We describe an embodiment in which the generator 200 is implemented at a base station of a wireless communication system capable of OFDMA communication. Generator 200 is capable of transmitting one or more OFDMA signals to one or more user terminals. Generator 200 includes a data buffer 210 capable of storing data addressed to one or more receivers. The data may be, for example, raw unencoded data or encoded data. Typically, data stored in the data buffer 210 is encoded and may include coding for error detection and forward error correction (FEC). The encoded data may be encoded according to one or more encoding algorithms. Encoding may include, but is not limited to, convolutional encoding, block coding, interleaving, forward spreading, coding with cyclic redundancy, and the like. or some other encoding.

The transmitted data is fed to a serial-parallel converter 212, which is able to convert the serial data stream stored in the data buffer 210 into a set of parallel data streams. The set of carriers allocated to any particular user terminal may be a subset of all available carriers. Therefore, data addressed to specific user terminals is converted into parallel data streams corresponding to the data carriers allocated to that user terminal.

The output of the serial-parallel converter 212 is supplied to a pilot signal module 220, which is capable of allocating common pilot channels to a common pilot signal and determining which of the user terminals will have one or more dedicated pilot channels. The pilot module 220 may be able to modulate each of the carriers of the OFDMA system with respective data or pilot.

The output of pilot module 220 is supplied to inverse fast Fourier transform (IFFT) module 222. OBPF module 222 is capable of converting OFDMA carriers to corresponding time-domain symbols. Of course, the implementation of the fast Fourier transform (FFT) is not a mandatory requirement, and for generating time-domain symbols, you can use the discrete Fourier transform (DFT) or some other type of transformation. The output signal of the IFFT module 222 is supplied to a parallel-serial converter 224, which is capable of converting parallel symbols of the time domain into a serial stream.

The serial OFDMA symbol stream is supplied from the parallel-serial converter 224 to the transceiver 240. In this embodiment, the transceiver 240 is a base station transceiver capable of transmitting forward link signals and receiving reverse link signals.

The transceiver 240 includes a transmitter module 244 that is capable of converting a serial stream of characters into an analog signal of an appropriate frequency for broadcast to user terminals via an antenna 246. The transceiver 240 may also include a receiver module 242 that is connected to the antenna 246 and is capable of receiving signals transmitted by one or more remote user terminals. Receiver module 242 may include a channel quality module 246 that is capable of receiving an indication of a channel quality estimate determined by one or more receivers.

The resource allocation module 230 is capable of determining which of the carriers for data transmission are assigned to each of the user terminals and which of the carriers should be allocated to the common and dedicated pilot signals. Resource allocation module 230 may include a common pilot module 232 capable of determining carriers allocated to a common pilot signal, a symbol module 236 capable of determining carriers allocated to data symbols for each user terminal, and a dedicated pilot signal module 234 capable of determine which, if any, of the carriers identified by the symbol module 236 should be configured as dedicated pilot signals. For example, resource allocation module 230 may determine a subset of carriers for allocation as data carriers for a particular user terminal based in part on a predetermined frequency hopping algorithm, according to another embodiment, resource allocation module 230 may determine a subset of carriers for allocation as carriers for data transmission for a specific user terminal based on the presence of a continuous block of carriers. Then, the resource allocation module 230 may adjust how data from the data buffer 210 is read into the serial-parallel converter 212 to provide support for frequency allocation.

Similarly, resource allocation module 230 may determine which of the carriers are allocated to a common pilot based on a predetermined common pilot algorithm. For example, resource allocation module 230 may be able to allocate resources to generate a stepped comb as a common pilot. A common pilot is typically used by user terminals to generate channel estimates and interference used in demodulating received symbols.

The resource allocation module 230 is also capable of allocating carriers for the allocated pilot signals. Initially, data transmitted to each user terminal may not include any dedicated pilot signals. However, one or more user terminals may not be able to decode the received signal. The user terminal may report to the generator 200 of unsuccessful demodulation. For example, the user terminal may send a retransmission request or an unsuccessful reception message to the receiver module 242 in the transceiver 240. Alternatively, the generator 200 may be able to determine that the user terminal was not able to successfully demodulate data if the ACK was not received within a predetermined period of time. A channel quality module 246 connected to the receiving module 242 can determine from the received signal, whether it is a channel quality signal, a retransmission request or the absence of an ACK message, a request for channel estimation resources.

The resource allocation module 230 may be connected to a channel quality module and is capable of receiving, for example, an indication of an unsuccessful demodulation and identifying a corresponding user terminal. Then, the resource allocation module 230 may be able to allocate additional channel estimation resources and interference to the user terminal in the form of dedicated pilot signals.

According to another embodiment, the resource allocation module 230 may be able to change the level of resources allocated to the common pilot or dedicated pilot in response to some other event or control signal. The resource allocation module 230 is not limited to changing resources allocated to a common pilot signal and a dedicated pilot signal based on feedback from one or more user terminals.

In one embodiment, receiving an indication of unsuccessful demodulation results in retransmission of data. Retransmitted data is re-encoded at a reduced data rate until it is stored in the data buffer 210. However, the use of a reduced data rate for retransmission is not required.

According to another embodiment, receiving an indication of unsuccessful demodulation leads to additional channel and interference estimation resources, but does not result in retransmission. Such an embodiment may be advantageous in time sensitive implementations where there is not enough time to retransmit unsuccessfully demodulated data.

According to one embodiment of increasing resource allocation, resource allocation module 230 allocates one of the data carriers for a user terminal to a dedicated pilot. The resource allocation module 230 may control the data buffer 210 so that data does not arrive at the serial-parallel converter 212 for a time corresponding to the carrier for transmitting data allocated to the dedicated pilot. The carrier assigned to the dedicated pilot may be modulated by one or more predetermined symbols allocated to the dedicated pilot. Alternatively, the carrier assigned to the dedicated pilot may remain unmodulated. The resource allocation module 230 may also control the pilot signal module 220 to clear, nullify, or otherwise substantially reduce the carrier power allocated to the allocated pilot. An empty pilot may be advantageous when a significant symbol power is normally allocated to each carrier for data transmission.

According to another embodiment, the resource allocation module 230 continues to provide data from the data buffer 210 to the serial-parallel converter 212 according to the allocation of carriers. However, the resource allocation module 230 controls the pilot module 220 to suppress data corresponding to the carrier allocated to the dedicated pilot. Data corresponding to a carrier allocated to a dedicated pilot may be discarded, or a carrier corresponding to a dedicated pilot may be omitted.

Resource allocation module 230 may continue to allocate the dedicated pilot to a specific user terminal until an indication of successful demodulation is received. If another indication of unsuccessful demodulation is received for the same user terminal for which the dedicated pilot is allocated, resource allocation module 230 may allocate one or more additional dedicated pilots for the user terminal. The resource allocation module 230 may thus dynamically allocate and allocate resources for channel estimation and interference based on the needs of a particular user terminal.

FIG. 2B is a functional block diagram of an embodiment of a receiver 202 capable of operating in an OFDMA wireless communication system having dynamically allocated channel estimation and interference resources. The receiver 202 may, for example, be part of a user terminal 110 or a base station 120a or 120b shown in FIG. We turn to the description of the receiver 202 implemented on the user terminal.

Receiver 202 may include an antenna 256 connected to a transceiver 250 capable of wirelessly communicating with a generator 200. Transceiver 250 may include a receiver module 252 capable of receiving wireless signals through an antenna 256 and generate a serial wideband symbol stream.

The output signal of the receiver module 250 of the transceiver 250 is fed to a serial-parallel Converter 260, capable of converting a serial stream of characters into a set of parallel streams corresponding to the number of carriers in the OFDMA system.

The output of the serial to parallel converter 260 is supplied to a fast Fourier transform (FFT) module 262. FFT module 262 is capable of converting time-domain symbols to corresponding frequency-domain symbols.

The output of the FFT module 262 is provided to a channel estimator 264, which is capable of determining the channel estimate and interference in part based on common pilots and any dedicated pilots. The carrier allocation module 280 determines the carriers assigned to the data, the carriers assigned to the common pilot signals, and the carriers, if any, assigned to the dedicated pilot signals. The carrier allocation module 280 is connected to the channel estimator 264 and informs the channel estimator 264 of the channel allocation.

Channel estimator 264 determines the channel estimate and interference in part based on common pilot signals, dedicated pilot signals, if any. The channel estimator 264 may determine the estimate using the least squares method, maximum likelihood estimate, combined least squares method and maximum likelihood estimate, and the like. or through some other process for channel estimation and interference.

The output of the channel estimator 264, including the result of converting the received symbols to the frequency domain and the channel and interference estimate, is supplied to the demodulator 270. The carrier allocation module 270 also informs the demodulator 270 of the carrier frequencies allocated for data transmission. Demodulator 270 is capable of demodulating received carriers for data transmission in part based on channel estimation and interference. In some cases, the demodulator 270 may be unable to demodulate the received signals. According to the above, the demodulator 270 may be unsuccessful because the channel quality is insufficient and cannot support the data transfer rate, or because the degradation due to an incorrect channel estimate and interference is so strong that it leads to a decoding error.

If the demodulator 270 is unsuccessful, it may generate an indication of the inability to demodulate the received signals. The demodulator 270 may, for example, inform the carrier allocation module 280 so that the carrier allocation module 280 can wait for the dedicated pilot in a subsequent transmission. The demodulator 270 may also indicate an unsuccessful demodulation to the transmitter module 254 of the transceiver 250 for transmission back to the generator 200.

If the demodulator 270 is unsuccessful, the received data is discarded, and therefore there is no need to send any data to the memory. If the demodulator 270 is successful, then the demodulator 270 may be able to provide demodulated data to the parallel-serial converter 272, which is able to convert the parallel demodulated data into a serial data stream. The output of the parallel-serial Converter 272 is supplied to the data buffer 274 for further processing.

FIG. 3 shows a frequency-time diagram 300 of an illustrative spectrum of an OFDMA communication system having an increase in resource allocation in the form of an increase in dedicated pilot signal inclusion. The time-frequency diagram 300 illustrates an example OFDMA system in which carrier blocks 310a-310f are assigned to each user in the system. A number of common pilot signals indicated by 'P', for example 320, are present at each time period, but do not necessarily appear in each carrier block 310a-310f. In addition, common pilots, for example 320, are not assigned to the same carrier in each time period, but follow a predetermined algorithm. Each receiver determines the channel estimate and interference in part based on all common pilot signals. However, typically only a receiver having a dedicated pilot in its carrier block uses a dedicated pilot in addition to common pilots in determining channel estimation and interference. In some embodiments, other receivers may be able to receive dedicated pilot signals outside the carrier block and use them to determine channel estimates and interference.

For example, at time t _{0, the} first carrier block 310a includes one common pilot and no dedicated pilot. However, the receiver assigned to the first carrier block 310a uses all common pilot signals in determining the channel estimate and interference. Similarly, the other receiver assigned to the carrier block 310d, at time t _0, has no common pilot in its carrier block 310d, but estimates the channel and interference using all common pilot signals.

In this example, at time t _{1, the} receiver assigned to the carrier block 310d has a dedicated pilot signal 331a. Thus, at time t _{1, the} receiver assigned to the carrier block 310d determines the channel estimate based on the dedicated pilot signal 331a in addition to all common pilot signals 321a through 321d. The advantage is that the dedicated pilot, 331a, is always in the carrier block assigned to the receiver. Thus, the channel estimate and interference obtained using the specified pilot signal is likely to be more accurate than the estimate obtained from the pilot signals outside the assigned carrier block.

It follows from the diagram that at time t _{2, the} receiver assigned to the carrier block 310d has two dedicated pilot signals 332a-332b. Such a situation may occur, for example, when the receiver is unable to demodulate the signals provided at time t ₁ and informs the generator of unsuccessful demodulation. The generator then provides the receiver with additional dedicated pilot signals. From the diagram it follows that the number and location of the allocated pilot signals can vary in each time period. Dedicated pilots typically do not affect receivers not designated as carriers for a dedicated pilot.

In other embodiments, it may be advantageous to reduce the resources allocated for channel estimation and interference. Such a situation may be useful when the receiver is sufficiently capable of estimating the channel and interference based on resources below the base layer, or may use the previous channel and interference estimate. For example, at time t _{1, the} receiver assigned to the carrier block 310g normally has a common pilot signal present in the carrier block. However, if the receiver indicates to the generator a sufficiently high signal quality, one or more pilot resources in the carrier block 310g can be omitted and data symbols may be transmitted instead of the pilot signals. In this case, reducing channel estimation resources and interference can improve system performance.

Reducing resources does not necessarily mean reducing total pilot resources. For example, at time t _{1, the} receiver assigned to the carrier block 310b deletes the dedicated pilot that appeared in the previous time period. Thus, a combination of dedicated and common pilot resources may fall under resource reduction. According to one embodiment, the transmitter may determine that the receiver has a signal quality that exceeds a predetermined threshold. The receiver may, for example, transmit the signal quality metric back to the transmitter. In this case, the transmitter may reduce the amount of resources allocated to the receiver.

FIG. 4A is a flowchart of an embodiment of a method 400 for allocating resources for channel and interference estimation. The method 400 may be implemented, for example, on a forward link of the base stations 120a-120b shown in FIG. In other embodiments, the method may be implemented on the reverse link of user station 110 shown in FIG.

For ease of explanation, method 400 is described with reference to a forward link implementation of a base station. The method 400 begins at block 410, where the base station assigns core resources for channel estimation. The base station proceeds to block 412 and transmits symbols and basic resources for channel estimation and interference to one or more receivers.

The base station then proceeds to decision block 420 to determine if all receivers successfully received and demodulated the transmitted symbols. If yes, then there is no reason to allocate additional resources for channel estimation and interference, and the base station returns to block 410.

If at least one receiver was unable to successfully demodulate the transmitted symbols, the base station proceeds to block 422 and determines which of the receivers was unsuccessful. After the base station identifies a failed receiver, for example, using retransmission requests or no ACK messages, the base station proceeds to block 430 and adds channel estimation resources to the failed receivers. Additional resources may be in the form of additional shared resources or dedicated resources. Additional shared resources may be less desirable as they may unnecessarily degrade channel capacity on receivers that do not experience any demodulation problems. Therefore, it may be advantageous to allocate dedicated channel estimation resources as additional resources. After the base station allocates additional resources, it returns to block 410.

FIG. 4B shows an embodiment of a method 402 for receiving symbols and channel and interference estimation in a system having dynamically allocated resources for channel and interference estimation. The method 402 shown in FIG. 4B is an embodiment complementary to the method 400 shown in FIG. 4A.

Method 402 may be implemented on a reverse link of a base station or on a forward link of a user terminal. FIG. 4B shows a forward link implementation of a user terminal in addition to the description given with reference to FIG. 4A.

Method 402 begins at block 440, where the user terminal receives broadcast symbols. The user terminal proceeds to block 450 and determines the main channel estimation resources allocated in the system. The user terminal then proceeds to block 452 and determines whether any additional resources have been allocated by the system for channel and interference estimation.

In the case where the additional resources are shared resources added due to the fact that another receiver requested resources, the user terminal may use additional shared resources for its channel and interference estimation. In the case where the additional resources are allocated channel and interference estimation resources, the user terminal may use the allocated resources only if the user has access to the allocated resources. This restriction usually requires the user terminal to request resources in advance.

Having determined the availability of additional resources, the user terminal proceeds to block 460 and determines the channel estimate and interference based on the available resources. Having determined the rating, the user terminal proceeds to block 470 and attempts to demodulate the received symbols partially based on the rating.

The user terminal then proceeds to decision block 472 and determines whether the receiver of the user terminal successfully demodulated the received signals.

If the user terminal determines successful demodulation, then the user terminal proceeds from decision block 472 back to block 440 to receive additional symbols. If, at decision block 472, the user terminal determines that the symbols have not been successfully demodulated, the user terminal proceeds to block 480 and requests additional resources for channel estimation and interference.

The request may be explicit, i.e. the user terminal transmits a request for additional channel estimation resources. Alternatively, the request may be implicit, i.e. the user terminal requests retransmission of unsuccessfully demodulated data. To implement an implicit request to the user terminal, it is not even necessary to send a transmission. For example, a user terminal may refuse to send an ACK in case of unsuccessful demodulation. Lack of ACK may mean a request for retransmission, and may also mean requesting additional resources for channel estimation and interference.

After the user terminal requests additional resources, explicitly or implicitly, the user terminal returns to block 440 to receive the transmitted symbols. In the case of a request for retransmission, the transmitted symbols may be a retransmission of previously received symbols that were unsuccessfully demodulated.

5 is a flowchart of an embodiment of a method 500 for allocating channel estimation resources in an OFDMA wireless communication system by turning on a pilot signal. The method 500 may be implemented, for example, by the base station shown in FIG. 1, on the forward link or by the user terminal shown in FIG. 1, on the reverse link. We proceed to a description of the method 500 carried out by the base station.

The method 500 begins at block 510, where the base station initially determines a set of common pilots, a set of dedicated pilots, or a combined set of common pilots and dedicated pilots dedicated to channel and interference estimation. The common pilot signal may be, for example, a step pilot or a combination of a step pilot and one or more separate pilots, and the base station may determine the carriers that are allocated for channel and interference estimation up to each OFDMA symbol or any or another interval.

The base station then proceeds to block 520, where it determines a set of symbol frequencies. The base station can simultaneously support several user terminals, and each of the user terminals can be allocated a subset of the available carriers remaining after the allocation of the carriers of the common pilot signals. The base station may allocate a different number of carriers as carriers for transmitting data destined for each of the active user terminals.

The base station then proceeds to decision block 530 and determines whether the base station has received a request for additional resources for channel estimation and interference for any of the user terminals. If not, the base station proceeds from decision block 530 to block 540, where the base station extracts data for each of the carriers in the frequency set for each of the user terminals.

If, at decision block 530, the base station determines that one or more of the user terminals requested additional channel and interference estimation resources, then the base station proceeds from decision block 530 to block 550. At block 550, the base station determines which of the carriers in the set carriers allocated to each of the user terminals are to be replaced by a dedicated pilot. The base station then proceeds to block 560 and extracts data for each of the subcarriers in the frequency set not allocated to the allocated pilot signals. If one or more of the data carriers is allocated to the dedicated pilot, then the base station may leave the carrier unmodulated or may clear or otherwise clear the carrier of the dedicated pilot.

The base station then proceeds to block 570 and determines the OFDMA symbol for user terminals. The base station proceeds to block 580 and transmits symbols, then returns to block 510 and prepares the next symbol.

FIG. 6 is a flowchart of an embodiment of a method 600 for receiving data in an OFDMA system having dynamically allocated channel estimation resources. The method 600 may be implemented, for example, on the forward link of the user terminal shown in FIG. 1, or may be implemented on the reverse link of the base station shown in FIG. Turning to the description of the method 600 implemented at the user terminal, in addition to the previous description of the base station with reference to FIG.

The method 600 begins with block 610, where the user terminal determines which of the carriers is allocated to the common pilot signal. Having determined the set of common pilot signals, the user terminal proceeds to block 620 and determines which of the remaining carriers is allocated for communication with the user terminal.

After determining the frequency set of the symbol, the user terminal proceeds to decision block 630 and determines whether additional channel estimation resources and interference are present in the symbol. The user terminal may determine the availability of additional resources as a result of a previous request for additional resources or may learn about the availability of additional resources based on a previous inability to demodulate received data. For example, in a HARQ system, a base station may automatically retransmit data if the user terminal does not issue an ACK. In addition, the retransmitted data may have a reduced coding rate and may include dedicated channel estimation and interference resources according to a predetermined algorithm. For example, for each retransmission, the coding rate may decrease with a predetermined coefficient, and the dedicated pilot may be included in the retransmitted data.

If additional dedicated pilot resources are available, the user terminal proceeds from decision block 630 to block 640 and determines which of the carriers is allocated to the dedicated pilot. According to the foregoing, the user terminal may determine which of the carriers is allocated to the dedicated pilot based on a predetermined algorithm. Then, the user terminal proceeds to block 650.

If, at decision block 630, the user terminal determines the absence of additional dedicated pilot signals, then the user terminal proceeds to block 650. At block 650, the user terminal determines the channel estimate based on the allocated resources. The user terminal may determine the channel estimate and interference solely on the basis of a common pilot signal. However, in the presence of dedicated pilots, the user terminal may determine the channel estimate and interference based on a combination of the dedicated pilots and common pilots.

Having determined the channel estimate and interference, the user terminal proceeds to block 660 and attempts to demodulate the signal using the previously determined estimate. The user terminal proceeds to decision block 670 and determines whether the received signal has been successfully demodulated.

If the received data is successfully demodulated, then the user terminal moves back to block 610 to prepare for the next character. Alternatively, if the user terminal at decision block 670 determines that the received data has not been successfully demodulated, then the user terminal proceeds to block 680 and requests additional dedicated pilot signals to further improve channel estimation and interference of subsequently received data.

Optionally, the user terminal may go to block 690 and request a retransmission. In some embodiments, a retransmission is not requested. Instead, unsuccessfully demodulated data is discarded. As noted above, in a HARQ system, retransmission may occur if the user terminal fails to send the ACK. In some embodiments, the retransmission request and the request for additional pilot signals are the same message or no message. After the retransmission request, the user terminal proceeds back to block 610 to prepare for the next character.

A system, apparatus, and method for dynamically allocating resources for channel and interference estimation has been disclosed. In an OFDMA system, dynamic resource allocation can be implemented as increasing pilot signal inclusion. Increasing the pilot signal can be implemented in the form of dedicated pilot signals so that the performance of other users is not reduced by adding resources.

Additional resources allocated for channel estimation and interference can only lead to a small loss in performance of a device having additional resources, especially if the allocated resources are added in the form of code punching of retransmissions that are provided at a reduced data rate or coding rate. The performance gain due to the increase in evaluation resources can be significant and can more than justify the increase in evaluation resources.

The various illustrative logical blocks, modules, and circuits described in connection with the embodiments disclosed herein may be implemented or implemented by a general purpose processor, digital signal processor (DSP), reduced instruction set processor (RISC), application specific integrated circuit (ASIC), Field Programmable Gate Array (FPGA) or any programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof and designed to carry out the functions described here. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, for example, a combination of a DSP and a microprocessor, a combination of microprocessors, one or more microprocessors in combination with a DSP core, or any other such configuration.

The steps of a method, process, or algorithm described in connection with the embodiments disclosed herein may be implemented directly in hardware, in a software module executed by a processor, or in a combination of the two.

The program module may be stored in RAM, flash memory, non-volatile memory, read-only memory, EPROM memory, EEPROM memory, in registers, on a hard disk, a removable disk, a CD-ROM, or any type of storage medium known in the art. An illustrative storage medium is connected to the processor, which allows the processor to read information from the storage medium and write information to it. Alternatively, the storage medium may be integrated in the processor. In addition, various methods can be carried out in the order shown in the embodiments, or can be carried out using a modified order of steps. Additionally, one or more steps of a process or method can be omitted, or one or more steps of a process or method can be added to the methods or processes. An additional step, block or action can be added to the beginning, end or between existing elements of methods or processes.

The above description of the disclosed embodiments is provided so that any person skilled in the art can use the disclosure. Various modifications of these embodiments are also apparent to those skilled in the art, and the general principles set forth here are applicable to other embodiments without departing from the spirit and scope of the disclosure. Thus, the disclosure is not limited to the embodiments shown here, but corresponds to the broadest scope consistent with the new principles and features disclosed herein.

Claims (44)

1. A device for dynamically allocating resources for channel estimation, the device comprising
a channel quality module capable of determining a request for channel estimation resources, and
a resource allocation module that communicates with the receiver and is capable of determining a basic resource level and a variable resource level, wherein the variable resource level is based at least in part on a request for channel estimation resources, and
the variable resource level contains a dedicated pilot signal, which is subjected to code perforation per data symbol. 2. The device according to claim 1, further comprising a transmitter connected to the resource allocation module and capable of transmitting a signal, a portion of which is allocated for channel estimation based on the main resource level and variable resource level. 3. The device according to claim 1, wherein the request for channel estimation resources comprises a retransmission request. 4. The device according to claim 1, in which the channel quality module determines the channel estimation request partially based on the presence or absence of an acknowledgment message. 5. The device according to claim 1, in which the main resource level contains a common pilot signal. 6. The device according to claim 1, in which the main resource level
contains a second dedicated pilot signal, which is coded perforated by a second data symbol. 7. The device according to claim 1, in which the variable resource level contains an additional pilot signal. 8. A device for dynamically allocating resources for channel estimation, the device comprising
a common pilot module capable of determining a first subset of carriers from a set of orthogonal code division multiple access (OFDMA) carriers, wherein the first subset of carriers is allocated to the common pilot,
a symbol module capable of determining a second subset of OFDMA carriers allocated to the communication channel, wherein the second subset of OFDMA carriers is different from the first subset of OFDMA carriers,
a dedicated pilot module capable of extracting at least one carrier from a second subset of OFDMA carriers for channel estimation,
a symbol generator capable of generating an OFDMA symbol from OFDMA carriers, and
a transmitter capable of transmitting an OFDMA symbol having dedicated pilots allocated for channel estimation, the extracted pilots being encoded into data symbols. 9. The apparatus of claim 8, wherein the dedicated pilot module is further capable of eliminating at least one carrier from a second subset of OFDMA carriers. 10. The device according to claim 8, in which the symbol generator contains an inverse fast Fourier transform module (IFFT). 11. A device for channel estimation based on dynamic resource allocation, the device comprising
a receiver capable of receiving an orthogonal frequency division multiple access (OFDMA) symbol, and having resources allocated for channel estimation,
a conversion module connected to the receiver and capable of converting the OFDMA symbol into a set of carriers,
a carrier allocation module capable of determining a first subset of carriers corresponding to the common pilot signal, a second subset of carriers corresponding to carriers for data transmission, and at least one carrier from a second subset of carriers corresponding to the allocated pilot signal,
a channel estimator connected to the transform module and the carrier allocation module, and capable of determining the channel estimate partially based on the common pilot signal and the extracted pilot signal, the extracted pilot signal being subjected to code perforation to the data symbol of one of the data carriers, and
a demodulator capable of demodulating carriers for data transmission in part based on a channel estimate. 12. The device according to claim 11, in which the conversion module comprises a fast Fourier transform (FFT) module. 13. The device according to claim 11, in which the selected pilot signal contains an empty pilot signal. 14. The device according to claim 11, in which the selected pilot signal contains a carrier modulated by at least one predetermined symbol. 15. The apparatus of claim 11, wherein the channel estimator is further capable of determining an interference estimate in part based on a common pilot signal and a dedicated pilot signal. 16. A method of generating a signal having dynamically allocated channel estimation resources, the method comprises the steps of:
assign the main level of channel estimation resources, determine the request for additional resources,
allocate additional resources for channel estimation, while the stage of allocating additional resources is that
a) determining a predetermined number of carriers from a set of orthogonal code division multiple access (OFDMA) carriers corresponding to data carriers, and
b) configure at least one of the carriers for data transmission as a dedicated pilot signal, and the selected pilot signal is subjected to code perforation on the data symbol of one of the carriers for data transmission, the signal is generated partially based on the main resource level and additional resources . 17. The method according to clause 16, in which at the stage of the assignment of the main resource level allocate a predetermined number of carriers from the set of orthogonal code division multiple access (OFDMA) carriers to the common pilot signal. 18. The method according to 17, in which when allocating a predetermined number of carriers allocate a predetermined number of carriers based on a predetermined algorithm. 19. The method according to clause 16, in which at the stage of the assignment of the main resource level allocate a predetermined number of carriers from the set of orthogonal code division multiple access (OFDMA) carriers to the second dedicated pilot, the second dedicated pilot being subjected to code perforation per symbol data of one of the carriers for data transmission. 20. The method according to clause 16, in which at the stage of determining the request for additional resources receive a request for retransmission. 21. The method according to clause 16, in which at the stage of determining the request for additional resources determine an unsuccessful transfer. 22. The method according to clause 16, in which at the stage of determining the request for additional resources determines that the message acknowledgment is not received within a predetermined period of time. 23. The method according to clause 16, in which the selected pilot signal contains a carrier modulated by at least one predetermined symbol. 24. The method according to clause 16, in which the selected pilot signal contains an empty pilot signal. 25. The method according to clause 16, in which at the stage of signal generation generate a symbol of multiple access orthogonal frequency division (OFDMA), having a first subset of carriers, providing the main level of resources, and a second subset of carriers, providing additional resources. 26. A method of processing a signal having dynamically allocated channel estimation resources, the method comprising the steps of:
process an orthogonal frequency division multiple access (OFDMA) symbol,
determining a core resource level for channel estimation included in the OFDMA symbol,
determining additional channel estimation resources included in the OFDMA symbol, wherein the step of determining additional resources is to determine at least one data carrier corresponding to the allocated pilot signal, wherein the extracted pilot signal is subjected to code perforation for the data symbol this at least one carrier for data transmission,
determining a channel estimate based on a core layer and additional channel estimation resources, and
demodulate the received symbol in part based on the channel estimate. 27. The method according to p. 26, in which when determining the basic level of resources, channel estimates determine the carriers corresponding to the common pilot signal. 28. The method according to p, in which when determining additional resources for channel estimation, at least one carrier corresponding to the empty pilot signal is additionally determined. 29. The method according to p, optionally containing stages, in which
determine whether the received symbol was successfully demodulated, and request additional channel resources if the received symbol was not successfully demodulated. 30. The method according to clause 29, in which at the stage of requesting additional resources transmit a request for retransmission. 31. The method according to clause 29, in which at the stage of requesting additional resources it is not possible to transmit an acknowledgment message. 32. A method for generating a signal having dynamically allocated channel estimation resources, the method comprising the steps of:
determining a set of common pilot signals from a set of orthogonal code division multiple access (OFDMA) carriers,
determining a set of symbols from a set of OFDMA carriers, determining a request for additional channel estimation resources, designating at least one carrier from a set of symbols as a dedicated pilot, wherein the extracted pilot is coded perforated onto a data symbol of at least single carrier for data transmission,
modulate character set carriers with data except for at least one carrier designated as a dedicated pilot; and
an OFDMA symbol is generated from the set of OFDMA carriers. 33. A method for generating a signal having dynamically allocated channel estimation resources, the method comprising the steps of:
assign a basic resource level for channel estimation, determine a receiver signal quality metric that exceeds a predetermined threshold,
determine the resources to be excluded from the main resource level, and
they generate a signal partially based on the main resource level having data symbols allocated to resources excluded from the main resource level, and these resources excluded from the main resource level contain a dedicated pilot signal, which is subjected to code perforation for data symbols. 34. The method of claim 33, wherein the resources excluded from the main resource level comprise a common pilot signal. 35. A device for generating a signal having dynamically allocated channel estimation resources, the device comprising
means for assigning a core level of channel estimation resources,
means for determining a request for additional resources, means for allocating additional resources for channel estimation, comprising
a) means for determining a predetermined number of carriers from a set of orthogonal code division multiple access (OFDMA) carriers corresponding to data carriers, and
b) means for reconfiguring at least one of the carriers for data transmission as a dedicated pilot signal, which is subjected to code perforation on a data symbol of one of these carriers for data transmission, and
signal generation means partially based on the main
level of resources and additional resources. 36. The device according to clause 35, in which the means for assigning a basic level of resources contains means for allocating a predetermined number of carriers from a set of orthogonal code division multiple access (OFDMA) carriers to a pilot signal. 37. The device according to clause 35, in which the means for determining the request for additional resources contains means for processing the request for retransmission. 38. A device for generating a signal having dynamically allocated channel estimation resources, the device comprising
means for assigning a core resource level for channel estimation,
means for determining a receiver signal quality metric that exceeds a predetermined threshold,
means for determining resources to be excluded from the core resource level, and
signal generating means, in part, based on the main resource level having data symbols allocated to resources excluded from the main resource level, the resources excluded from the main resource level containing a dedicated pilot signal, which is subjected to code perforation for the data symbol. 39. The apparatus of claim 38, wherein the resources excluded from the main resource level comprise a carrier from an orthogonal frequency division multiple access (OFDMA) system assigned to a common pilot. 40. An apparatus for dynamically allocating resources for channel estimation, the apparatus comprising
memory, and
a processor capable of determining a basic resource level and a variable resource level, wherein the variable resource level is based at least in part on a request for channel estimation resources, the main resource level containing a dedicated pilot signal that is subjected to code perforation for a data symbol. 41. The apparatus of claim 40, wherein the processor is capable of determining a channel estimate request in part based on the presence or absence of an acknowledgment message. 42. The device according to p, in which the main resource level contains a common pilot signal. 43. The device according to p, in which the variable resource level contains an additional pilot signal. 44. The device according to p, in which the variable resource level contains a second dedicated pilot signal, which is subjected to code perforation for a second data symbol.

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