CN1184751C - Method for improved wireless optical communication and frames for use in wireless optical communication system ` - Google Patents

Abstract

The present invention relates to a wireless optical communication method between a transmitting station and a receiving station. The transmitting station supplies a request to send (RTS) frame to the receiving station to inform that a data frame is transmitted, when the request to send (RTS) frame is correctly received, the receiving station provides a clear to send (CTS) frame for the transmitting station, and the transmitting station subsequently sends the data frame to the receiving station. The RTS frame comprises a preposition segment (PA), a synchronous segment (SYNC), a brute force header segment (RH), a source address / destination address segment (SA/DA) and a cyclic redundancy check segment (CRC). The power level of the RTS frame is regulated to specified transmitted power level of different transmitter data frame, and then, the present invention permits the link quality evaluation with large dynamic ranges and improves collision avoidance characteristic by the variable repeating codes in the brute force header segment (RH) of the RTS frame. Some one power level which can be higher than or below the specified transmitted power level of the data transmission can be selected, a plurality of different adding possibility of the connection between the stations can be improved according to the repeating codes of the selected power level, and the protection can be required.

Description

Improved wireless light communication method

Technical field

The present invention relates generally to optical communication system, relate in particular to link-quality and link-quality estimation between dispatching station and the receiving station.

Background technology

For infrared equipment communication, infrared data association (IrDA) has delivered a series of permissions are carried out data communication between the equipment that utilizes infrared (Ir) medium specification.The paper that F.Gfeller and W.Hirt1997 delivered in the IrDA of Toronto meeting at April 17 " strive ask suggestion for senior infrared (AIr) physical layer specification " has been described the notion of Robust Headers (powerful title RH), provide reliable conflict to avoid with infrared media interviews control (IrMAC) agreement, this agreement is responsible for coordinating between the infrared equipment visit to infrared medium.In the title of physical layer, use RH, when keeping conflict to avoid characteristic, the coexistence that allows to have different angles and scope characteristic.

The publication number of on January 3rd, 1996 application is that International Patent Application PCT/IB96/00002 of WO97/25788 has described a kind of optical communication system, can communicate between the transmission of several coexistences and receiving station.In order between the coexistence station, to communicate, used the physical layer title (being referred to as powerful title RH here) that can add inbound a kind of brute force of understanding for all.

Two above-mentioned publications have formed the present situation of basis of the present invention and this technology, are quoted for reference here.

According to these reference documents, infrared equipment adopts the mode of equity to communicate, wherein, dispatching station provides request to send (RTS) frame and gives receiving station, notice will send packet, and receiving station offers this dispatching station at least with a clear to send (CTS) frame under the situation that correctly receives the RTS frame, and dispatching station sends to receiving station with Frame subsequently.According to the requirement of general IrMAC frame format, RTS frame and CTS frame comprise a preamble field (PA), a synchronization field (SYNC) and a powerful title (RH) field at least.The PA field allows to carry out reliable carrier sense, symbol clock is synchronous and the chip clock phase obtains, and reaches low-down signal to noise ratio (snr).The PA field comprises the symbol that forms pulse period series, the groove number of each symbol (L-serrated pulse position modulation for example; Offer 4-groove (4-PPM) coding of AIrPHY), and to add inbound to all be known symbol content.The SYNC field also is a field with legal 4-PPM series of symbols, can discern the beginning of RH field exactly and comprise the legal 4-PPM symbol of predetermined some.According to the above-mentioned file of quoting, the RH field comprises the field of several regular lengths and known structure.By these fields, can notify the relevant data transmission used communication means to receiving station.In addition, these fields also are used to communication link or information exchange that other control information is provided, and permission is coordinated the data transfer rate that is used to send and regulated, so that optimize throughput according to quality of channel.

According to above-mentioned IrDA meeting paper, the RTS frame further comprises address field, and it is called source address and data address (SA/DA) field, and address field is in RH field back.And the RH field always utilizes repeated encoding to carry out the brute force coding, and the speed stipulations (RR=16) of employing 16 provide maximum detection sensitivity.RR has defined the rank of repeated encoding, so that guarantee correct transfer of data; Therefore, each symbol is repeated RR time.Redundancy in the symbols streams that causes thus plans to adopt in the demodulator circuit suitable digital processing method to be developed, and provides SNR gain with the cost that reduces the 4/RRMb/s data rate.This is equivalent to electric receiver bandwidth of independent coupling and the data rate that is lowered.With the contrast of the method for this complexity, the method that is proposed adopts a kind of virtual bandwidth reducing and does not need to change physically the bandwidth of receiver here, therefore can adopt and the simple of the basic rate-matched of 4Mb/s and the receiver embodiment optimized.The RR factor is defined as value 1,2,4,8 and 16, and wherein the RR=1 correspondence has 4-PPM and do not have the basic speed of the 4Mb/s of repeated encoding.The available data rate of the RR factor value of being defined is 4,2,1,0.5 and 0.25Mb/s.Each stipulations level provides the SNR that is rated for the electric unit of 3dB gain, and corresponding luminous power is the gain of 1.5dB.Therefore, along with RR changes to 16 from 1, specified SNR gain correspondingly is increased to the electric unit of 12dB from 0dB.Note that the remainder in the application, relative power stage will adopt photometric units to measure.The electric relatively power of the corresponding 2XdB of relative optical power level XdB or the relative SNR of 2XdB change.The general data speed of the 0.25Mb/s of RR=16 must be supported by all systems in certain subelement of certain communication unit or certain communication unit.This data rate is used in each RH field that is sent out frame, and is used for transmitting the information of relevant MAC and PHY layer.Along with the raising of data rate stipulations, communication system can be operated under the SNR condition of variation in succession.This can be used for enlarging range of transmission, compares with the basic rate of 4Mb/s, can reach 2 times range of transmission at 0.25Mb/s, perhaps under hostile channel condition, under for example very strong background light, keeps the quality of link.In addition, repeated encoding has reduced the adverse effect of interference signal, and can carry out power management by use higher data speed in than short distance, and it is minimum that the energy consumption that makes each be sent out frame thus reaches.

Compare with the RTS frame, the CTS frame finishes with the RH field.The RH field of CTS frame comprises a RR ^*Field rather than RR field, the RR field in this field and the RTS frame is similar, difference is its suggestion, according to the assessment of this link-quality or some other indication oppositely use RR.Thus, target device suggestion source device should use this parameter when communication.

According to the paper of IrDA meeting, Frame adds a body field after PA, SYNC and RH field, and this field comprises a big data field, and the back is followed a Cyclic Redundancy Check field again.Crc field is variable repeated encoding 32 bit fields, adopts well-known method to check whether transmission is successfully finished.

The frame that adopts prior art is with single fixing luminous power and uses fixing RR to send in title.This just is unable to estimate the link-quality of the 4Mb/s data rate (corresponding RR=1) that has short bag, for example RTS and CTS frame.In addition,, the parity mismatch condition that may occur do not handle leeway for providing enough SNR.Note that in the paper that IrDA meeting that the parity notion of Ir system has been quoted in the above delivers and introduced.

Summary of the invention

Therefore general objects of the present invention be in the notion of AIr, for add inbound between improved conflict avoid characteristic and link-quality assessment that a solution is provided.

Therefore further purpose of the present invention provides a kind of method, if selected RR satisfies the SNR of certain defined, then guarantees only to set up a contact between the station.

Another object of the present invention provides solution, for specific frame is introduced in the link-quality analysis.

Further purpose of the present invention provides a kind of energy-conservation pattern.

As mentioned above, the present invention is exactly in order to satisfy these purposes.It provides a kind of method of carrying out wireless light communication between dispatching station and receiving station, by this, dispatching station provides the RTS frame to receiving station, notice will send packet, receiving station is under the situation that correctly receives the RTS frame, the CTS frame is offered this dispatching station, and dispatching station sends to receiving station with Frame subsequently.Note that the CTS frame that sends from receiving station is sent to the dispatching station that sends the RTS frame at least.Two kinds of frames (RTS and CTS) all comprise PA field, SYNC field and the RH field of general requirement.The RTS frame further comprises at least one a source address/DAF destination address field (SA/DA) and a cyclic redundancy check field (CRC).By the variable repeated encoding in the powerful title division (for example RTS frame), the power stage of RTS frame and/or CTS frame is adjusted to specified transmit power level when being different from Frame and being sent out, allows the dynamic range of a bigger link-quality assessment and the conflict that is modified and avoid characteristic.Dependence can be than the specified transmission power level height or the low selected optical power level of data transmission; and rely on a variable repeated encoding that depends on selected optical power level; proposed to improve and added the some different possibility that connects between inbound, and claimed to this.

The CTS frame has higher power stage but does not have variable repeated encoding (being RR=16), for example, can increase the range of transmission of cts signal to packet, that is, the terminal of hiding can be found better, and conflict can more effectively be avoided.

According to a most preferred embodiment, the RTS frame is sent out with the constant transmission power level less than specified transmit power level, the speed stipulations RR=16 of RH field, the variable R R=1 of SA/DA field and crc field subsequently, 2,4,8 or 16.Select transmit power level, combine, make receiving station on average, obtain being correctly decoded of SA/DA field desired SNR with selected SA/DA field.Transmit power level is preferably in 50% to 75% the scope of specified transmit power level.

According to another embodiment of the invention, the RH field of RTS frame comprises that distinguishing son field for one (finds field; DISC), specify the RTS frame to find frame, and comprise a broadcast destination address in the SA/DA field as one.This allows to have process finding frame and uses the RR value that progressively increases that is sent by dispatching station, receives answer from receiving station up to it.

In a further most preferred embodiment, adopt the transmit power level higher to send the field of RTS frame and CTS frame than rating data transmit power level.In addition, the RTS frame comprises the afterbody that has a trailer field (TR) at least, and this field is followed in the crc field back, has the power stage lower than nominal power level.The power stage of the described RH field of described RTS frame and RR correspondingly are selected to produce equal detection sensitivity, i.e. RR=16 and specified power stage.Therefore, the RTS field comprises two different power stages at least.A purpose of this method is to reduce the total length of RTS frame, and another purpose is to increase the dynamic range that link-quality is analyzed by the illegal 4-PPM symbol in the counting end segment.May use RR=2,4 or 8, they have corresponding high power level, provide and RR=16 and the equal detection sensitivity of rated power.By adopting the 4.5dB that increases with respect to normal light power, the optical power level of 3dB or 1.5dB and using respectively equals 2,4 or 8 RR value and satisfies this condition.The high power level of RTS/CTS field is the twice of rated power preferably, so RR=4.And in another embodiment, the lower-wattage level of at least one TR field is half of rated power preferably, because this means reduce 3dB on luminous power, when using when pressing the variable light power stage of 1.5dB step change, this is an optimum value.

Be not equal to 16 for fixing RR, RR=4 for example, the pattern in the described SYNC field is squeezed with respect to mode standard, so that notice receiving station; The RTS frame will be sent out with different fixedly RR values (RR=4 here), and this value is known for adding inbound.

Another most preferred embodiment that can be used for assessing link quality has used afterbody, comprises the several TR fields with different capacity level, and different optical power levels is preferably from the nominal power level of twice, reduce step by step by the step-length of 1.5dB.

For (about 0.5m distance) reduction electric power consumption when sending data on a very short zone, and with the RTS of reduction and the optical power level of CTS is that member's (station) increases data throughout, just send Frame according to a further embodiment, this embodiment has the optical power level less than nominal power level, and, variable repeated encoding in need not the powerful title division of described RTS/CTS frame, but with respect to mode standard the SYNC field is inverted so that the power stage of a reduction to be described.

Description of drawings

Below, the present invention will be described in detail in conjunction with following accompanying drawing, wherein

Figure 1A has provided a new RTS/DISC frame, half of the nominal power level when it has the transmission Frame, and have the SA/DA and the crc field of variable repeated encoding (RR=1,2,4,8 or 16);

Figure 1B has provided a new RTS frame that has the power stage of twice and have the afterbody of half power stage, the CTS frame with twice power stage, and the normal data frame with nominal power level;

Fig. 2 has provided an embodiment, detects dissimilar frames by inverted SYNC series;

Fig. 3 represents according to the LQA of the RTS frame of Figure 1B (link-quality analysis);

Fig. 4 has provided another RTS/DISC frame with afterbody, and this afterbody comprises 4 slope-shaped power stages;

Fig. 5 represents according to the LQA of the RTS frame of Fig. 4 (link-quality analysis);

Fig. 6 has provided a further RTS/DISC frame of the afterbody with the slope-shaped power that is modified;

Fig. 7 has provided another RTS/DISC frame that has afterbody, and this afterbody has power stage and the RR=8 of half; And

Fig. 8 provides a DISC frame with constant nominal power level, has the afterbody that is encoded of RR=16.

Embodiment

Different application is described below, and the power stage that these application can be controlled RTS frame and/or CTS frame is different from the specified transmit power level when sending Frame, and carries out variable repeated encoding at least in the powerful title division of RTS frame.Operation has required conflict and avoids an essential requirement of the RTS/CTS media access protocol of characteristic to be to use powerful title, detect the transmission frame that sends from various device with the detection sensitivity that strengthens, and, set up the correlation of infrared channel for each equipment that adds the RTS/CTS agreement according to the definition of above-mentioned IrDA meeting paper.

When RR=16, the distance that frame is sent out reaches uses identical power and the twice of transmission range during RR=1.Therefore, RR=1 can save energy in short distance, because its frame is shorter.Can guarantee during RR=16 to repeat 16 times, therefore the Frame that is sent out will be not easy to be interfered, but its frame becomes longer.RR=1 is than the equivalent difference of RR=16 corresponding to 4 times of transmitted powers.Sending the RTS frame is for the notification data frame will be sent to certain specific receiving station, and the transmission range of RTS frame should be the same with the transmission range of the Frame that is added into long.The transmission range of CTS frame (being sent by the station that receives the RTS frame) should be long as far as possible, so that the link that handle is set up with dispatching station is notified other station.By increase in specific application or minimizing power stage, and further variable repeated encoding, the especially repeated encoding of RTS frame, the distance of transmission and the quality of link just can be influenced.

An embodiment of new RTS frame shown in Figure 1A, comprises criteria field PA, SYNC and RH, and SA/DA field and crc field are followed in the back.The optical transmission power stage of this frame is constant, 50% to 75% of the nominal power level when being about the Frame transmission.The RH field comprises the son field of usual PHY and MAC layer, comprises son field RR, is SA/DA and crc field indication repeated encoding subsequently.The RH field itself is 16 times a repeated encoding (being RR=16), so that obtain maximum detection sensitivity.The SA/DA field is the same with CRC all to be handled as the short data field, all uses identical RR=1, and 2,4,8 or 16 encode.Select the RTS through-put power like this, be combined into the RR value that the SA/DA field is selected, make Target Station obtain be correctly decoded (the carrying out verification) of SA/DA field on average to certain required SNR by the common method of CRC employing.

The purpose of this method is that the frame of being lost by burst frame (for example from the very poor station of the parity of transmitter) is obtained the leeway that compensates.For this reason, suppose that be known for sending packet to the desired RR value in certain specific station.Send RTS with half of rated power, its transmission range is about 0.71 of the distance that sends with rated power, and therefore, if distance is longer, SA/DA is forced to become false when then arriving receiving station.On average, Frame uses rated power when sending, and can guarantee the leeway that its channel is fairly good and can afford redress to interference.If the SNR of this link is enough good for data packet transmission subsequently, promptly, coming the test link quality with the SA/DA field, then send RTS with the power that reduces and with above-mentioned RR SA/DA and crc field are encoded, just can only be correct to the CRC check of SA/DA field.Here do not use the symbol error counting.If it is incorrect that CRC detects, just do not send CTS.So, if be used for that the SNR of certain regulation of selecteed RR is satisfied then this method guarantees Target Station only responds the sender of RTS with CTS.By select an extraordinary SNR with the cost of accessible transmission range, just can obtain the leeway that above-mentioned compensated frame is lost.

Each station that adds certain multi-terminal network (communication unit or subelement) all requires to know the quality of link between itself and the every other station.Can carry out link-quality analysis (LQA) and when frame is exchanged, upgrade, for example, described in above-mentioned WO97/25788.In addition, the station that adds certain activity network must be notified oneself all entrants and must carry out mutual LQA.This can accomplish that on principle as WO announces, yet this method must realize with software (IrMAC).In order on the basis that can carry out the speed coordination, to replenish this LQA method, under several situations, for example, when certain new station adds certain network that has existed, perhaps all when adding its LQA table of inbound renewal when requiring, require to obtain LQA result faster.

Therefore, in another embodiment, use identical frame structure and transmitted power, but in the RH field, have different son fields and in da field, have broadcast destination address.Utilize this son field among the RH, the RTS frame is designated as one and finds frame (DISC).Not to specific equipment addressing, so the RTS/DISC frame signals to all stations in the da field here.In order between certain second unknown but potential B of receiving station of first A of dispatching station and the address of listening to the radio programme, to connect, the RTS/DISC frame the when A that stand sends the RR=1 with the short transmission scope of correspondence with SA/DA and CRC.B can decode to SA/DA with correct CRC if stand, and it will be with confirming that the acknowledgement frame so that RR=1 receives responds.The A that stands sends to station B with rated power and RR=1 with Frame subsequently.B can not decode to SA/DA with correct CRC if stand, and does not then send and replys.In this case, the A that stands sends the discovery frame with the RR=2 of corresponding certain longer scope.After receiving answer, the A that stands sends packet with corresponding RR.A does not receive answer if stand, and will continue to send the discovery frame with the RR value that progressively increases, up to the response or the RR=16 (maximum range of transmission) that obtain from station B.Because can receive more than one of the station of the RTS/DISC frame that the A that arrives at a station sends, therefore, these stations all utilize well-known " compensation " method to answer, in this method, each stands in before the answer, waits for time cycle of selection at random.This has reduced the danger of CTS frame conflict.

The purpose of RTS frame is that notice will send a Frame.Require the range of transmission of RTS frame identical, for example RR=16 with the maximum range of transmission of maximum length Frame.In order to make the time window minimum of potential conflict, the RTS frame should be short as far as possible.Therefore, according to a further embodiment, in order to obtain short RTS frame, the optical transmission power of RTS frame increases with 3dB or 1.5dB, the normal light through-put power of comparing data frame, and further the speed stipulations factor R R of RH field and SA/DA field is set to 4 or 8 respectively.In addition, shown in Figure 1B, the RTS frame with shorter length also can send RTS and have the dynamic range of the increase that is used for LQA by the power stage with twice.RTS frame as described herein comprises first section that sends with twice rated power, as what known, comprise PA, SYNC (being squeezed), RH, SA/DA and crc field, wherein, RH, SA/DA and CRC are the repeated encodings when RR=4, and the RTS frame also comprises second section with half transmission of rated power, comprise and have enough number 4-PPM symbols, for example 100, an afterbody (TR) field so that determine the quality of this link.Note that in Figure 1A and 1B the horizontal line of with dashed lines illustrates rated power (relative luminous power is consistent).

Figure 1B gives the power stage of CTS frame and Frame and selection thereof.For the CTS frame, the range of transmission (for example RR=16) that is hopeful to obtain an expansion improves its conflict under the situation of multiple terminals and avoids characteristic, and coordinates the tolerance in the IR channel correlation.This CTS frame has double rated power and one by the SYNC pattern of normal encoding (face as follows), and the RH coding with RR=16 is described.Notice that the SYNC pattern is also referred to as synchronization character.Normal encoding (RR=16) and variable-data-rate (RR=1,2,4,8 or 16) with normal light power, RH information send Frame.

Because receiving station does not also know the RH field with what RR value is encoded (except the frame of RR=16 always), require the pattern explanation of another signalling of employing to allow to be used for the different RR of this communication system.Dispatching station encodes to SYNC series with different polarity for this reason, this depend on this frame whether comprise with RR=4 (selected) or RR=16 as present embodiment (maximum, as above-mentioned quote defined) title/address information of encoding.If RTS encodes with RR=4, then the SYNC field comprises a synchronous mode that is squeezed and negative correlation peak of receiving station's detection.The appearance of this incident then is used to notify modulator-demodulator: will decode with RR=4 in powerful title/address.Fig. 2 provides an embodiment of this pattern, and wherein, a SYNC subfamily (hex ' OBEA64E3 ') is squeezed.The complete SYNC series that is sent out of method construct according to WO97/25788 described in open, difference is if necessary, and in these two series one is that first is squeezed here.In the SYNC field, according to second series (for example ++-+-) serial hex (0BEA64E3) or its inverted series are encoded, as WO open described in so that form the complete SYNC series that is sent out.In order to explain the present invention, first series is squeezed; In addition, second series (++-+-) also can be squeezed (--+-+).The SYNC field that receives judges that by the phase I associated factor 1, the digital quantizer 2 that are used for the SYNC detection, the second stage correlation factor 3 that is used for the SYNC detection and SYNC 4 handle.Therefore output signal have three possible values-1,0 or+1, represent respectively SYNC detected/RH: RR=4, do not have SYNC detected and SYNC is detected/RH: RR=16.Therefore, the SYNC field is illustrated as inverted SYNC field among the RTS/DISC shown in the part of Fig. 2 lower left.

As already mentioned, the TR field allows the LQA dynamic range of an increase by to illegal 4-PPM symbol count.According to the definition of L-groove PPM (L-PPM), illegal symbol means that the TR field that is received comprises or do not have pulse, and the symbol more than one pulse that is caused by noise is perhaps arranged.Method based on the prior art of the illegal L-PPM symbol of the counting described in the WO97/25788 is only used a power stage to all frames.This does not allow the link-quality of the Frame that uses RR=1 is assessed, because the symbol of energy usefulness can not obtain satisfied measurement very little in the RTS frame.If have the extraordinary link-quality of permission with the maximum data rate operation of RR=1, then in short-tail portion series, may detect less than illegal symbol, if but have long data bag (being 2048 bytes to the maximum), then mistake also may take place, and therefore can require to adopt RR=2 to send.1/2 power stage artificially in the TR field increases error count, make an increase and more accurate error count appear in the afterbody.For given tail length (number of 4-PPM symbol), between possibility that illegal symbol occurs and link-quality (SNR in dB), there is a relation that is defined (Fig. 3).Therefore, the TR field in the present embodiment comprises 100 4-PPM symbols that send with 1/2 normal light power.The power stage that is lowered has been strengthened invalid 4-PPM symbol (mistake), and this can detected and counting.By tabling look-up desired RR ^*Value can be determined and be sent back to dispatching station by the CTS frame.

Now in conjunction with Fig. 3 with general terminological interpretation LQA.Following function is (also the seeing Figure 1B) of being correlated with:

1. the RH that receives and the illegal L-PPM symbol among the SA/DA are counted, carry out verification and send utilization hardware threshold value with the power that increases with CRC.

2. the illegal L-PPM symbol in the TR field is counted utilization hardware threshold value.

3. determine recommended speed stipulations factor R R according to the number (error count) of illegal L-PPM symbol ^*, and with RR ^*Insert the CTS frame and do not need the intervention of IrMAC (part of software protocol stack).

4. suitably select to determine RR ^*The error count number of L-PPM symbol (=illegal) threshold value so that obtain enough SNR, for example work as RR=RR ^*The time, sending success rate is 99%.If assess the SNR that obtains according to the RTS frame that receives when RR=16, be not enough to support for example 99% error-free data transmission, just there is not the CTS frame to be sent back.Minimum required link SNR is set up in reliable transmission when this is RR=16.

Fig. 3 is according to the RTS frame of Figure 1B, and two different power stages with respect to nominal reference (REF.Pnom) are described, and (2Pnom, Pnom/2), invalid 4-PPM symbol is as the possibility of the function of SNR.This figure shows, detects 100 symbols, for RR=1 (point of sign X on reference curve) and nominal power level Pnom, can not get significant error count.As an example, can expect to have the error count of 100 detected symbols according to the point of representing on the curve.The point of SNR is expressed, and requires the frame of 512 bytes to be obtained 90% successful transmission rate with nominal power level Pnom.Can be 16 bytes and 2048 bytes foundation point separately.According to these reference points, can determine error count scope and definition threshold value, be used in the RR that determines to insert the CTR frame in the practical implementation then ^*, as mentioned above.For the SNA between the 5-10dB, preferably using is the mistake (imaginary curve A and B) that two power stages are obtained.This has the SNR that helps distinguish more than the 10dB.

Can produce afterbody with an above power stage.Its advantage is can make the more property curve be used for error count and can be measured more accurately.An advantage of this method is to make afterbody series become longer (seeing the comparison of Figure 1B and Fig. 4).Yet the RTS frame is still short than the RTS frame of prior art.As shown in Figure 4, the RTS frame comprises the power ramping afterbody with 4 different capacity levels.For example,, be suitable for using 5 optical power levels, the be separated by step-length of 1.5dB of adjacent each for AIr equipment.This provides 5 error counts that have equal statistical property in the scope of whole SNR.In the SA/DA field and in the sub-afterbody of each TR field subsequently, 128 symbols are sent out and 100 symbols are used to error count (allowing 28 symbols to be used to be provided with gain control circuit).This pattern is illustrated in Fig. 5.Same threshold when its expression is counted different capacity level estimation error (5-10 wrong).Error count to the adjacent power level also can be used for certain given power stage so that improve the SNR assessment more.For determining RR ^*And the quality of assessment link by on different power stages each sub-afterbody being counted illegal symbol separately, to certain given length of each sub-afterbody, is determined required RR ^*, 100 symbols for example.For example, sub-afterbody provides 5-10 wrong error count, and its explanation is based on the required RR of curve shown in Figure 5 ^*Value.

Fig. 6 and Fig. 7 further provide the mutation according to new RTS/DISC frame of the present invention.Even the notion here is only to use 2 and 3 power stages, also utilize signal processing in the modulator-demodulator to obtain the equivalent of 5 different capacity levels respectively.For example, in Fig. 6, can obtain the power stage P2 (1.5dB light) that loses virtually, too by before the illegal 4-PPM symbol of counting, detecting afterbody 1 valuation with RR=2 for the power stage P4 that loses.Here in each sub-afterbody, 228 symbols are sent out and 200 symbols are used to error count (RR=1 and RR=2).In Fig. 7, by with RR=2, RR=4 and RR=8 detect the afterbody evaluation, obtain the error count with power stage P4, P3 and P2 equivalence respectively.Detect P1 and P5 evaluation with RR=1.In the present embodiment, the TR field comprises 828 4-PPM symbols that send with RR=8, and 800 symbols are used to error count, with respectively to RR=1,2,4 and 8 average detected.

Fig. 6 and RTS frame shown in Figure 7 also can be used as finds frame (DISC frame), as top discussed.Just in case there is not specific equipment to be addressed, the DA record among Fig. 6 and Fig. 7 sends signal to all stations, and all stations can be carried out LQA and therefore adjust its LQA table sending address SA.This " signal emission " method can be carried out by hardware.

Just in case have only a power stage can use (hardware constraints), the available afterbody RR=6 that is encoded uses the discovery frame among Fig. 8.By at first reducing the sensitivity of receiving station, for example adopt 9dB (electric SNR) to obtain 5 virtual power levels of LQA, utilize RR=1 then, 2,4 obtain the error count of the different optical power levels of corresponding 5 1.5dB of being separated by with 16 average detected.In addition, can come the sensitivity of controlling receiver by the changes of threshold in the determining apparatus.

In another embodiment, can use the same number of frames type of being introduced in the described IrDA meeting publication document, but will be to reduce and constant optical power level, for example with 5% power save mode of rated power down during operation, to all above-mentioned certain SYNC patterns that is squeezed of frame type use.Adopt this method, when (about 0.5-1 rice) sends data on a very short distance, can reduce the consumption of power, and the member of formed " picocell " (being also referred to as subelement) be increased the throughput of data.When SYNC pattern that use is squeezed, receiving station can't detect the existence of frame from the distant station that adopts normal SYNC pattern operation.Therefore, can catch channel from subelement member's signal, this causes increasing data throughout.On the other hand, very little from subelement member's transmitting power, therefore also minimum to the interference of other distant stations.

Claims (17)

1. method of between dispatching station and receiving station, carrying out wireless light communication, wherein

Described dispatching station will ask transmit frame to offer described receiving station, will send Frame with notice,

Under the situation that correctly receives the request transmit frame, described receiving station provides the clear to send frame for described dispatching station, and

Described dispatching station sends to this receiving station with certain specified transmit power level with Frame subsequently,

The described request transmit frame comprises preamble field, synchronization field, powerful header field, source address/DAF destination address field and cyclic redundancy check field, the described request transmit frame is sent out with first optical power level, and powerful header field utilizes the first rate stipulations to carry out repeated encoding, therefore, perhaps

Described first optical power level is higher than described specified transmit power level, and described first rate stipulations are lower than maximum speed stipulations, perhaps

Described first optical power level is lower than described specified transmit power level, and described first rate stipulations equal described maximum rate stipulations.

2. the process of claim 1 wherein that described first optical power level is lower than described specified transmit power level, and first rate stipulations 16 are used to described powerful header field.

3. the method for claim 2, wherein, the second speed stipulations 1,2,4,8 or 16 are used to the transmission of source address/DAF destination address field and cyclic redundancy check field subsequently.

4. the process of claim 1 wherein, suitably select described first optical power level,, guarantee to reach the predefine reliability that between described dispatching station and described receiving station, sends so that in conjunction with described first rate stipulations.

5. the method for claim 3 wherein, is suitably selected first optical power level, so that in conjunction with the described second speed stipulations of source address/DAF destination address field, receiving station obtains its correct decoding to required signal-to-noise ratio on average.

6. the method for claim 2, wherein, first optical power level is in 50% to 75% scope of specified transmission power level.

7. the process of claim 1 wherein that described powerful header field comprises that is distinguished a son field, it specifies the described request transmit frame as the discovery frame, and also comprises a broadcast destination address in described source address/DAF destination address field.

8. the method for claim 1, wherein, employing is higher than described first optical power level of described specified transmit power level, send the described preamble field of described request transmit frame and described clear to send frame, synchronization field and powerful header field, and the described request transmit frame further comprises the afterbody that has a trailer field at least, this field is in the cyclic redundancy check field back of request transmit frame, has second optical power level that is lower than described specified transmit power level, select described first optical power level and described first rate stipulations accordingly, so that produce the detection sensitivity that equates with speed stipulations 16 and specified transmit power level.

9. the method for claim 8, wherein, described first optical power level is the twice of specified transmission power level, and wherein said first rate stipulations are 4.

10. the method for claim 8, wherein, half that described second optical power level of described at least one trailer field is specified transmit power level.

11. the process of claim 1 wherein that described synchronization field comprises the pattern that is squeezed with respect to certain standard synchronous mode, so that different speed stipulations are described.

12. the method for claim 8, wherein, described afterbody comprises the several trailer fields with different optical power levels.

13. the method for claim 12, wherein, described different optical power levels begin from the twice of specified transmission power level, with the step-length minimizing of 1.5dB.

14. the method for claim 1, wherein, in order to reduce power consumption, the 3rd optical power level that employing is lower than described specified transmit power level sends described request transmit frame and described clear to send frame, and wherein, in described synchronization field, use inverted standard synchronous mode that the 3rd optical power level of minimizing is described.

15. the process of claim 1 wherein that described clear to send frame also comprises preamble field, synchronization field and powerful header field.

16. the method for claim 15 wherein, adopts an optical power level that is different from described specified transmit power level to send described clear to send frame.

17. the process of claim 1 wherein that described Frame is repeated coding.

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