Method and apparatus for data communications over multiple channels

(Priority claim under 35 USC 119) This patent application states "METHOD AND APPARATUS FOR DATA COMMUNICATIONS OVER MULTIPLE CHANNELS". Titled, the priority of the US provisional patent application with serial number 60 / 511,275, filed October 14, 2003, assigned to its assignee, and expressly incorporated herein by reference. Insist.

(Field) The present invention generally relates to data packet communication, and more specifically to communication on multiple channels.

A wireless communication system for packet data transmission typically establishes one channel type between the transmitter and the receiver when the packet is ready for transmission. This type of channel is used for signal path and control between a base station (BS) and a mobile station (MS), but can also carry user or application data. Since this channel is shared among several receivers, it is usually slow and the transmitter is designed to be received by the receiver in the poorest channel condition. This channel is called the common channel.

Wireless communication systems have another type of channel that can be used primarily for user or application data, which is faster and more efficient. This is the preferred channel for sending data from the transmitter to the receiver. This type of channel needs to be set up before data can be sent into it. The setup process is time consuming and causes delays throughout the system. The transmitter or receiver can initiate a fast channel setup. This channel is called the dedicated channel.

Both channels have different attributes with respect to speed and latency. Multiple types of channels are available for communication links between base stations and mobile users. Each type of channel may have different attributes with respect to speed, latency, robustness, capacity, and other quality of service (QoS) goals. When an application has different quality goals for services and a communication system has multiple channels with different attributes, the question arises of how to best transmit data over the multiple channels. Applications may require low-delay data transmission, especially when only slow channels are currently readily available. Such applications may require the speed capacity of fast channels; however, the addition of fast channels generally results in additional setup time.

Therefore, in the present technology, there is a need to process communication with multiple channels that support different attributes. In addition, there is a need to provide communication for service applications of various qualities using slow and fast channels, or other channels with different attributes and characteristics.

[wrap up]

The embodiments disclosed herein are methods for communicating low-delay data over multiple channels, each with different speed and latency characteristics, and each requiring a different amount of time to set up. And by providing an apparatus to meet the above needs. This disclosure avoids other configurations and handles issues related to multiple channel types, as well as the order at the receiver when data packets are sent by the transmitter over multiple channels with variable attributes. Demonstrates a technology and equipment that eliminates the problem of out-of-order and duplicate data packets.

[Detailed description]

The features, objectives, and advantages of the methods and devices now disclosed will become more apparent from the detailed description provided below along with the drawings.

The increasing demand for wireless data transmission and the expansion of available services through wireless communication technologies have led to the development of specific data services. One such service is called HDR. Examples of HDR-type systems are the "CDMA high-rate packet data air interfaces" called the "HAI specification" and "TIA / EIA / IS-856". It is proposed in the "cdma2000 High Rate Packet Data Air Interface Specification".

HDR subscriber stations, referred to herein as access terminals (ATs), may be mobile or fixed, and can communicate with one or more HDR base stations, here referred to as modem pool transceivers (MPTs). The access terminal can send and receive data packets through one or more modem pool transceivers to and from an HDR base station controller, here called the Modem Pool Controller (MPC). Modem pool transceivers and modem pool controllers are parts of a network called an access network. The access network transports data packets between multiple access terminals. The access network can also be connected to additional networks outside the access network, such as the corporate intranet or the Internet, and data packets can be transmitted between each access terminal and such an outside network. An access terminal that has established an active traffic channel connection with one or more modem pool transceivers is an active access terminal. It is called an active access terminal) and is said to be in a traffic state. An access terminal in a process that is establishing an active traffic channel connection with one or more modem pool transceivers is said to be in a connection setup state. The access terminal can be any data device that uses, for example, a fiber or coaxial cable and communicates over a wireless or wired channel. Access terminals can also be any of many types of devices, including but not limited to PC Cards, CompactFlash®, external or internal modems, or wireless or wireline telephones. Good. A communication link in which an access terminal sends a signal to a modem pool transceiver is called a reverse link. The communication link that the modem pool transceiver sends a signal to the access terminal is a forward link (a). It is called forward link).

FIG. 1 shows an embodiment of an HDR system for communication between BS100 and a plurality of MSs (multiple MSs) 110 and 120. A common channel 140 exists between multiple MSs 110, 120 and 1BS100. Dedicated channel 130 exists between MS110 and BS100. Similarly, a dedicated channel 150 exists between the MS120 and BS100. The system can incorporate multiple common and dedicated channels in wireless communication systems. Both types of channels can be used for user data and control information between base stations and mobile stations. The present disclosure uses HDR examples as an example. Other embodiments can include any system with multiple channels between the transmitter and receiver. In addition, term channels can be applied to channels separated by frequency, sign, time, or space. In addition, channels can be shared between users as in the case of common channels.

In HDR, an example of a common channel on a forward link (FL) for communication from a base station to a mobile station is a "control channel". On the reverse link (RL) from a mobile station to a base station, an example of a common channel is an "access channel". Examples of dedicated channels are forward and reverse traffic channels.

FIG. 2 is a system model of a communication system having multiple channels between a transmitter 200 and a receiver 210. Channel 220 and channel 230 have different set-up and transmission attributes, respectively. This model allows the ideas of this disclosure to be applied to both FL and RL, where in FL the transmitter 200 is BS and the receiver 210 is MS, and in RL the transmitter. 200 is MS and receiver 210 is BS.

In particular, a common channel 220 already exists between the transmitter 200 and the receiver 210 when the packet is ready for transmission. However, the common channel 220 is also designed so that the transmitter on the common channel 220 is received by the receiver in the poorest channel state because it is shared among several receivers. Because it is, it is slower than the dedicated channel 230. Moreover, since it operates at the lowest data rate, less data is sent over the common channel 220.

To save power, the receiver can choose not to constantly monitor the common channel 330 and only go into wakeup mode at some point to verify that the data is available ( only wake up at certain times), if no data is available, the receiver returns to sleep mode.

FIG. 3 illustrates the transmission of data on the common channel 330 and on the dedicated channel 340. As illustrated, a page message is sent from transmitter 300 to initiate the set up of dedicated channel 340, causing a time delay to complete the setup. Since the transmitter 300 knows when the receiver monitors the common channel 330, the transmitter 300 sends a page at an appropriate time. If the page or data is sent to the receiver when the receiver (not shown) is not monitoring the common channel 330, then the receiver will not receive the data and system resources will be wasted. ..

Once the dedicated channel 340 is set up, data should be sent using this channel. Dedicated channel 340 is a more efficient, faster, higher capacity channel and is preferred for user or application data. Furthermore, if user or application data is sent using both the common channel 330 and the dedicated channel 340 after the dedicated channel 340 is established, the relative ordering of the data sent across the two channels is It needs to be maintained and increases the processing at the receiver. In addition, once the dedicated channel 340 is set up, the receiver will continue to monitor the dedicated channel 340. Therefore, the dedicated channel 340 is a preferred channel for sending data from the transmitter 300 to the receiver. However, the dedicated channel 340 is not always ready for use. Dedicated channel 340 needs to be set up before data may be sent on it. The setup procedure takes time. Since the common channel 330 is always available, it is used to set up the dedicated channel 340. Either the transmitter 300 or the receiver can activate the setup for dedicated channel 340.

Under normal operation, when data arrives at transmitter 300, transmitter uses common channel 330 to send control messages or pages to the receiver with packet data 310 that causes the setup of dedicated channel 340. Once the dedicated channel 340 is set up, the data is transferred to the receiver in packet data 320 using the dedicated channel 340. Normal operation is sufficient for most applications that have delay tolerant data. The above description applies only to forward links. On the reverse link, the transmitter will send a connection request over a common access channel to set up a dedicated traffic channel.

As an example, transmitter 300 can now transmit on common channel 330, thus sending page message 310 at time t1. Transmitter 300 sends page 310 over common channel 330 to initiate the setup of dedicated channel 340. Accordingly, the receiver can send a connection request message, where the transmitter 300 and the receiver negotiate the setup of a dedicated channel 340. After the setup delay, transmitter 300 can send data over dedicated channel 340, eg packet 320 at time t2.

Transmitters are required to carry time-sensitive data that, based on the application, must arrive at the receiver within a certain delay. Maybe. For time-sensitive data, as shown in Figure 4, it is not desirable to wait for the dedicated channel 430 to set up before the data is sent to the receiver. In this scenario, the transmitter 400 sends the data in the packet data 410 on the common channel 420 and at the same time starts the set-up of the dedicated channel 430 (time t1). Control information that sets up the dedicated channel 430 can be sent on the common channel 420 or by any other available channel. This allows for early transmission of data. Once the dedicated channel 430 is ready (time t2), the data is sent over the dedicated channel 430.

FIG. 5 is a block diagram showing packet data communication on multiple channels after the MS510 sends a communication request to the transmitter 500. As shown in FIG. 5, once the MS510 requests a connection and a dedicated channel 550 is established in response, the transmitter 500 uses the more efficient channel, the dedicated channel 550, to provide packet data. Start sending more data in 520. However, one problem that arises is that the duplicate packet data 520 is sent on both channels 540 and 550 because the packet data 520 was already scheduled to be sent on the common channel 540. Is.

Figure 5 illustrates the possibility of receiving duplicate data. That is, the packet data 520 can be queued for transmission on the dedicated channel 550. Once the dedicated channel 550 is established, the packet data 520 will be scheduled for transmission. Packet data 520 is also sent on a common channel with page 514. This provides the potential for low latency transmission on the common channel 540 while maintaining the correct sequence order on the dedicated channel 550. However, for many applications the packet data has already been scheduled on a common channel, which may cause further delays, so such a technique is a problem with multiple packets at the receiver. cause.

FIG. 6 is a timeline illustrating out-of-order packet transmission. Time-sensitive data, that is, delay-sensitive data, arrives at the transmitter at time t1. At time t2, the transmitter schedules packet 1 to be transmitted over the common channel at time t6 and also sends a control message to initiate the setup of the dedicated channel. As described above, when the receiver monitors the common channel, packet 1 can be sent to the receiver at the next opportunity. At time t3, the receiver wakes up up), request a connection and start setting up a dedicated channel. At time t4, the dedicated channel is ready; it should be noted that this is before the data is transmitted over the common channel. After setting up the dedicated channel, the transmitter sends the next packet, packet 2, at time t5 on the dedicated channel. Packet 2 sent on the dedicated channel arrives at the receiver before packet 1 is sent on the common channel at time t6 (as scheduled by the transmitter at time t1). The data thus arrives at the receiver out-of-order. This scenario is shown in the timeline of Figure 6 using a message consistent with the HDR standard as an example. Receiving out-of-order packets is a problem for many applications. For example, out-of-order packets in streaming audio or video applications may result in sound or video distortion, respectively. In addition, duplicate packet data increases the delay time.

FIG. 7 is a timeline of one method of removing out-of-order or duplicate packets. Delay-sensitive data arrives at the receiver at time t1. At time t2, the transmitter schedules the transmission of packet 1 on the common channel at time t6, and also initiates the procedure for setting up a dedicated channel. Again, the receiver sends a connection request to the transmitter to initiate the setup of the dedicated channel. If packet 1 is ready for use by the dedicated channel before packet 1 is scheduled for transmission on the common channel at time t6, the transmitter then removes packet 1 from the common channel queue. At time t5, packet 1 is sent over an established dedicated channel. Following this procedure, the transmitter calculates the timing and, at the appropriate time, removes packet 1 from the queue on the common channel.

Alternatively, if the transmitter knows how long it will take to establish a dedicated channel (eg, the time it takes for the dedicated channel to prepare the data), the transmitter will receive packet 1 when the receiver receives packet 1. You can decide, and by doing so, remove packet 1 from the queue on the common channel to avoid duplication.

According to the embodiment illustrated in FIG. 7, the transmitter first determines the setup time for a dedicated channel. Setting up a dedicated channel requires some communication and negotiation between BS and MS using already established channels, such as common channels, and can therefore be difficult to predict. unknown. Therefore, the transmitter may have difficulty deciding whether to remove packet 1 from the common channel queue to prevent duplicate or out-of-order transmissions.

Moreover, once the transmitter has calculated the set-up time and decides to remove the packet from the common channel queue, the transmitter may have difficulty removing the packet. This means, for example, if the transmitter has two entities, a base station controller (BSC) that creates a packet and queues it, and a base transceiver system (BTS) that maintains the queue and transmits the packet. ), If it consists of, it could happen. Since BSC is already communicating with BTS to carry packet data, it may not be possible to cancel the schedule.

According to another embodiment that avoids these two problems, the transmitter uses a sequence number to identify the packet, as illustrated in FIG. For example, packet 1 1050 carries sequence number 1, which is transmitted as sequence number 1040. Packet 1 1050 is transmitted over common channel 1020 as payload 1042 with sequence number 1040. Packet 2 1070 carries sequence number 2, which is transmitted as sequence number 1060. Packet 2 1070 is transmitted over dedicated channel 1030 as payload 1062 and sequence number 1060. If the receiver initiates the setup of the dedicated channel 1030, while the packet is scheduled to be transmitted over the common channel 1020, then if there is a setup of the dedicated channel 1030, the transmitter 1000 will Packet 1 1050 is transmitted on a dedicated channel, followed by packet 2 1060. If the receiver is packet 1 1050 and / or packet 2 If the 1070 is received through both the common channel 1020 and the dedicated channel 1030, the receiver will discard later arrivals as duplicates based on the sequence number. In this case, the packets arrive at the receiver in sequence and duplicates are discarded using the sequence number. This method also allows for reordering at the receiver. FIG. 10, which is the timeline of this procedure, shows packet data communication on multiple channels in which a duplicate packet is detected and removed by the receiver.

With respect to FIG. 10, a delay-sensitive packet arrives at the transmitter at time t1. At time t2, the transmitter schedules packet 1 to be transmitted over the common channel at time t6. At time t3, the receiver sends a connection request to set up a dedicated channel, and at time t4, the dedicated channel is ready for data. At time t5, the transmitter uses the dedicated channel to send packet 1 followed by packet 2 using the dedicated channel (and the receiver then receives it). Finally, at time t6, the transmitter sends packet 1 at time t6 using the common channel (and the receiver then receives it), and the receiver discards packet 1 on the common channel as duplicates.

FIG. 11 illustrates a case where the packet data 720 on the common channel 740 is discarded because it is a duplicate of the packet data 730 on the dedicated channel 750. Both packet data have the same sequence number, but do not necessarily have to be the same data. Since both packet data have the same sequence number, the MS710 can detect duplicate packet data.

In another embodiment, FIG. 12 is a phase diagram for a receiver processing data on a common channel. First, the receiver processes the data received on the common channel in state 800. At state 800, the receiver is ready to process data on the common channel. Once the data is received on the dedicated channel and once the data is successfully processed on the dedicated channel, the receiver transitions to state 810, resulting in the data received on the common channel being discarded. .. As long as a dedicated channel is available, the receiver will continue to ignore the common channel data. When the dedicated channel is released, the receiver transitions to state 800 and resumes processing data received on the common channel. Once the dedicated channel is set up to receive packet data, the receiver ignores the data on the common channel. When the dedicated channel is open and no data is received, it will not ignore the common channel and will be ready to process that data.

In certain embodiments, as illustrated in FIG. 13, DOSPs use signalized packets when communicating in systems that use multiple channels, such as common channel 1120 and dedicated channel 1130. The name given to the protocol that provides higher layer packets) transmission and duplicate detection. Upper layer packets, packets higher than radio layer packets, are carried in DOSP messages. This corresponds to the data transported on the common channel 1120. The common channel 1120 is typically used for signals, but in the case of DOSP messages sent over the common channel, the message carries data for the upper layers. DOSP also uses message sequence number 1140 in DOSP messages to provide duplicate detection.

The protocol data unit or transmission unit for this protocol is a DOSP message. DOSP messages also carry payloads 1150 and 1170 for the upper layers.

As illustrated in FIG. 8, the DOSP can be in one of two states, the inactive state 860 and the active state 850. Upon receiving a Data Over Signaling message, the receiver will validate the message. If it is invalid, it will discard the data over signaling message. If the message is valid, the receiver will pass the Higher Layer Packet field of the data over signaling message to the higher layer. Upon processing the received RLP packet, the receiver will transition to inactive state 860. The protocol is air-link management. Idle (an Air-Link Management. Upon receiving the Idled) instruction, the access terminal and access network will then transition to the active state 850. The receiver will discard the received data over signaling message.

FIG. 13 illustrates packet data communication using the DOSP format, where the payload in the common channel is discarded. With respect to FIG. 13, the active state is a state in which a message received on the common channel 1120, such as a data over signaling message 1150, is processed by the receiver. The receiver transitions to the inactive state after it has processed a Radio Link Protocol (RLP) message 1180 sent over dedicated channel 1130. RLP messages are used in wireless communication systems to carry higher levels of data over traffic channels. RLP1180 has sequence number 1160. If the receiver detects sequence number 1160 equal to sequence number 1140, then it will discard DOSP message 1150 on control channel 1120. That is, the receiver continues to process the RLP message and discards the payload of the DOSP message 1150 while it is inactive.

The sender sets the Message Sequence field of DOSP message 1150 to V (S). V (S) is a counter maintained by the sender to provide a message sequence. Each time the sender sends a DOSP message 1150, the sender increments the V (S) value.

As shown in FIG. 13, since the queued and potentially transmitted packets on the common channel 1120 use the DOSP1150 with the same sequence number space from the RLP packet 1180 sent on the dedicated channel 1130. The out-of-order duplicate packet problem is avoided. Once dedicated channel 1130 becomes available, packets that are queued and potentially transmitted over common channel 1120 are transmitted over dedicated channel 1130 and also using DOSP message 1150. After these packets are retransmitted on dedicated channel 1130, the remaining packets in the message are sent using the RLP 1180 with payload. Since the packets that are queued on the common channel 1120 and requeued on the dedicated channel 1130 have the same sequence number, the receiver can easily detect packets that are duplicated out of order.

In another embodiment, when active and receiving DOSP message 1150, the receiver confirms the message. The receiver receives an RLP packet 1180 with a payload on dedicated channel 1130, so it discards the payload of DOSP message 1150. If the message is valid, the receiver will pass the upper packet field of the DOSP message to the upper layer.

When processing the received RLP packet, the receiver transitions to the inactive state. The receiver discards the received DOSP message 1150 when it is in the inactive state.

In the inactive state, when the protocol receives an air-link management idle instruction, the access terminal and access network then transition to the active state 850, where it processes DOSP messages.

As described above, the BS or MS sends a DOSP message to carry the layer packet. The following table shows an example of the DOSP message format in this particular example.<tables num="1"><img file="JP2007508787A_D0001.tif" /></tables>

Message ID: The sender sets this field to 0x14. This parameter identifies a particular DOSP message.

Message Sequence: The sender sets this field higher than the message sequence field of the last (last) DOSP message it sent (256 modulo 256). This parameter corresponds to the sequence number.

Higher Layer Packet: The sender sets this field to an entire higher layer packet. For example, if the upper layer packet is a High Level Data Link Control (HDLC) frame, then the entire HDLC frame is included. The length of the upper layer packet may be an integer of octets. The sender assigns the priority of the message to the range of 20 to 50 (including 20, 50), depending on the priority of the upper layer packets carried as the payload in this message. This parameter corresponds to the data sent on the channel.

FIG. 14 is a block diagram of an embodiment of the transmitter device. The data source 1200 is any application that provides data transmission. Processor 1210 provides the queuing, formatting, and sequencing functions of the embodiments described in this disclosure. Processor 1210 also includes a scheduler 1240 for scheduling packet data transmissions on the channel. Transmitter 1220 includes signal formatting and modulation required for transmission. Finally, the data packet is transmitted using antenna 1230. It should be noted that various functions can be distributed or shared by blocks. For example, the queuing function can be distributed among both processors and transmitters. In addition, the data source 1200, processor 1210, and transmitter 1220 can be integrated into a smaller number of blocks, or they can be divided into a large number of blocks.

FIG. 15 is a block diagram of an embodiment of the receiver device. The RF signal is received by antenna 1330. The receiver 1300 demodulates the signal and supplies the processor 1310 with a symbol stream. Processor 1310 decodes the symbol stream into bits and also provides the functions of ordering, deformatting, and multi-channel reception described in the present disclosure. Processor 1310 also includes a duplicate detection unit 1340 for detecting duplicate packet data and a DOSP state machine 1350 for detecting the active and inactive states of the receiver as defined above. A data bitstream may be an application that needs data data sink (the data) It is supplied to sink) 1320. It should be noted that various functions can be distributed or shared by blocks. The receiver 1300, processor 1310, and data sink 1320 can be integrated into a smaller number of blocks, or they can be divided into a larger number of blocks.

Those skilled in the art will appreciate that the various steps or elements in the examples can be modified or their order can be rearranged without changing from the disclosed invention.

Those skilled in the art will appreciate that information and signals can be represented using any of a wide variety of different techniques and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be voltage, current, electromagnetic waves, magnetic fields or particles, light fields or particles, or any of these. It can be represented by a combination.

Those skilled in the art will appreciate the various explanatory logic block diagrams, modules, circuits, and algorithm steps described in connection with the embodiments disclosed herein as electronic hardware, computer software, or a combination of both. You will further understand that it can be done. To articulate this hardware-software interchangeability, various descriptive components, block diagrams, modules, circuits, and steps are generally described above in terms of their functionality. Whether such functionality is implemented as hardware or software depends on the design limitations imposed on the particular application and the entire system. A skilled craftsman may implement the described functionality in various ways for each particular application, but such implementation decisions are construed as causing deviations from the scope of the invention. Should not be.

The various descriptive logic block diagrams, modules, and circuits described in connection with the embodiments disclosed herein are general purpose processors, digital signal processors (DSPs), application specific ICs (ASICs), and field programmables. Performed or performed with a gate array (FPGA), or other programmable logic circuit, discrete gate or transistor logic, discrete hardware components, or any combination of these designed to achieve the functionality described herein. Can be done. The general purpose processor may be a microprocessor, but otherwise the processor may be any conventional processor, controller, microcontroller, or state machine. Processors are also implemented as a combination of arithmetic units, such as a combination of DSP and microprocessor, multiple microprocessors, one or more microprocessors in combination with a DSP core, or any other such configuration. Can be done.

The steps of the method or algorithm described in connection with the examples disclosed herein can be embodied in software modules executed directly by the processor in hardware or in combination of the above two. it can. Software modules reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disks, removable disks, CD-ROMs, or any other form of storage medium known in the art. You may. An exemplary storage medium is coupled to the processor so that the processor can read information from the storage medium and write the information to the storage medium. Alternatively, the storage medium may be built into the processor. The processor and storage medium may reside in the ASIC. The ASIC may reside in the user terminal. Alternatively, the processor and storage medium may reside as discrete components in the user terminals.

The above description of the disclosed examples is provided so that anyone skilled in the art can make or use the present invention. Various variations of these embodiments will be readily apparent to those of skill in the art, and the comprehensive principles defined herein can be applied to other embodiments without departing from the spirit or scope of the invention. .. Therefore, the present invention is not intended to be limited to the examples presented herein, and should be given the broadest scope consistent with the principles and novel features disclosed herein.

<figref num="1">FIG. 1 is a block diagram of an embodiment of a high data rate (HDR) protocol wireless communication system.</figref><figref num="2">Figure 2 shows a system model for multiple channel communication.</figref><figref num="3">FIG. 3 is a diagram showing packet data communication sent on multiple channels.</figref><figref num="4">FIG. 4 is a diagram showing packet data communication sent on one channel.</figref><figref num="5">FIG. 5 is a diagram showing multi-channel packet data communication when packets are received in duplicate after the MS sends a communication request.</figref><figref num="6">FIG. 6 is a timeline showing multi-channel packet data communication when packets are received out of order.</figref><figref num="7">FIG. 7 is a timeline showing multi-channel packet data communication when a packet is removed from a one-channel queue when another channel becomes available.</figref><figref num="8">FIG. 8 is a receiver phase diagram in the Data Over Signaling Protocol (DOSP).</figref><figref num="9">FIG. 9 is a diagram showing packet data communication in DOSP when the payload on the common channel is discarded.</figref><figref num="10">FIG. 10 is a timeline showing multi-channel packet data communication when duplicate packets are detected and removed by the receiver.</figref><figref num="11">FIG. 11 is a diagram showing multi-channel packet data communication when duplicate packets are detected and removed by the receiver.</figref><figref num="12">FIG. 12 is a receiver phase diagram for a receiver that processes data on a common channel.</figref><figref num="13">FIG. 13 is a diagram showing packet data communication in a typical DOSP.</figref><figref num="14">FIG. 14 is a block diagram of an embodiment of the transmitter device.</figref><figref num="15">FIG. 15 is a block diagram of an embodiment of the receiver device.</figref>