Abstract:
A way of implementing the Detect-and-Avoid (DAA) function into WiMedia/UWB devices based on the existing WiMedia protocol. The DAA operation is conducted in the MAC, and the MAC informs the software for the decision making process. 
     The DAA operation in this invention composed of two individual operations; the Interferer-Detection operation and the Avoid-Interference operation. 
     The Avoid-Interference operation follows the Interferer-Detection operation if the host MAC reports excessive error after the Interferer-Detection operation. 
     This invention suggests various ways of avoiding interferences with the existing services or with other UWB network

Description:
RELATED APPLICATIONS 
       [0001]    The present application is a continuation application of United States provisional patent application, serial number U.S. 60/753,753, filed Dec. 22, 2005, for METHOD OF DETECTING AND AVOIDING INTERFERENCE AMONG WIRELESS NETWORK BY DYNAMICALLY ESTIMATING THE NOISE LEVEL FROM THE UWB PER AND BER, AND SYNCHRONOUSLY SWITCHING INTO UNOCCUPIED CHANNEL, by Hyun Lee, included by reference herein and for which benefit of the priority date is hereby claimed. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention generally relates to the fields of home and personal wireless networking and, more particularly, to Wireless Home Area Networks or Wireless Personal Area Networks that are based on various standard communication protocols. 
       BACKGROUND OF THE INVENTION 
       [0003]    More than one communication network, whose signals are modulated with various methods, likely occupy a wireless communication space. Therefore, the interferences between these networks dictate the QoS of these networks. In development of the UWB (WiMedia) technology, the noise level simulation for the QoS study was based on the AWGN, and the transmit power and the receive sensitivity were controlled to preserve a certain level of QoS (8% packet-drop-rate with 1024 byte data). However, there was no attempt to ensure the interference it causes to the existing services by preserving its own QoS. This missing specification in UWB protocol that ensures the co-existence with existing services brought concerns to MIC (Japan) and CEPT (Europe), and they mandated the DAA requirement that must be met by any devices that are based on the UWB technology. 
         [0004]    Since the existing services may not use the same modulation scheme and protocol as the UWB protocol, it becomes real a challenge for the UWB manufactures to satisfy the DAA requirement. For example, since a UWB antenna cannot detect the narrowband signals of the existing services, the problem the UWB manufactures face is a much more fundamental issue, such as how to detect the existing service signals. A number of PHY companies put their effort on resolving this DAA issue, however, no PHY company had developed a working solution yet. 
         [0005]    The general solution that suggested by the PHY companies is; 
         [0006]    Multiple Physical layer Solution, for example, “Detect and Avoid Technology For Ultra Wideband (UWB) Spectrum Usage”—a white paper—Wisair Corporate. 
         [0007]    This solution requires multiple physical, one for the UWB operation and the others for detecting the narrowband and/or broadband signals. 
         [0008]    The idea is to use the narrowband or broadband antenna to detect the existing signals while using the ultra-wideband antenna for the UWB communication. The narrowband and/or broadband signal detection generally occurs during the quiet time of the UWB signal since the USB signal strength (˜−40 DBM) could be stronger than the signal strength of the existing signals, which could be less than −60 DBM. In some cases, when the existing signal strength is stronger than the UWB signal strength, the existing signals can be detected during the active UWB signal transmission. However, if the existing signal strength is stronger than the UWB signal, since the receiver can filter out the UWB signal, there is actually no need for the DAA operation. Therefore, the multiple-antenna solution is most effective in detecting the existing signal during the quiet period of the UWB signal. 
         [0009]    In addition to the limited usage, another shortcoming of this solution is from its requirement of holding any UWB traffic while detecting the existing services. This method may require a large number of antennas to parallelize the detecting effort. For example, to be able to detect the existing signal with one antenna, it would require 384 msec of UWB quite time, which can be many seconds of real time. This quiet time requirement is computed with the fact that it requires 1 msec of signal power integration time to make the correct decision on whether the broadband signal is the existing signal or noise. 
         [0010]    Thus, the total quiet time to determine the existing signal would be: 
         [0011]    1 msec (integration time)×128 (sub-carriers/UWB-frequency-band)×3 (bands/band-group-for OFDM)=384 msec. 
         [0012]    This detection time would be long enough to cause the existing signal to loose its connection. 
         [0013]    It is therefore an object of the invention to allow the UWB network to detect the existing service without additional narrowband/broadband antenna. 
         [0014]    It is another object of the invention to remove the requirement of having the PHY baseband processors to recognize the narrowband/broadband signals. 
         [0015]    It is another object of the invention to see the benefit even if this invention were implemented in only a limited number of devices (or one device) in the system. 
         [0016]    It is another object of the invention to allow detecting the existing services without integrating the RF power in each sub-carrier over 1 msec period, thus, significantly reducing the detection time. 
         [0017]    It is another object of the invention to allow this narrowband/broadband detection method to be applicable to any other wireless communication network in addition to the network using UWB. 
         [0018]    It is another object of the invention to allow the interference detection mechanism to be applicable to any communication protocol that uses UWB channel. 
         [0019]    It is another object of the invention to find the appropriate interference interferences avoidance procedure based on the results of the interference analysis. 
         [0020]    It is another object of the invention to minimize the duration of interfering the existing services. 
         [0021]    It is another object of the invention to resolve the interference issue with the minimum down time (quiet time) for the UWB network 
         [0022]    It is another object of the invention to effectively mitigate the interferences among a number of UWB networks whose physical spaces are overlapping each other. 
       SUMMARY OF THE INVENTION 
       [0023]    In accordance with the present invention, there is provided a way of implementing the Detect-and-Avoid (DAA) function into WiMedia/UWB devices based on the existing WiMedia protocol. The DAA operation is conducted in the MAC, and the MAC informs the software for the decision making process. 
         [0024]    The DAA operation in this invention composed of two individual operations; the Interferer-Detection operation and the Avoid-Interference operation. 
         [0025]    The Avoid-Interference operation follows the Interferer-Detection operation if the host MAC reports excessive error after the Interferer-Detection operation. 
         [0026]    This invention suggests various ways of avoiding interferences with the existing services or with other UWB network 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0027]    A complete understanding of the present invention may be obtained by reference to the accompanying drawings, when considered in conjunction with the subsequent, detailed description, in which: 
           [0028]      FIG. 1  is the impact of narrow band existing signal on the bit error rate (ber) as function of signal to interferer ratio (sir); 
           [0029]      FIG. 2  is the impact of narrow band existing signal on the average bit error rate (ber) as a function of average white gaussian noise (awgn) for different levels of sir; 
           [0030]      FIG. 3  is a block diagram of the encoding process for the payload in a uwb packet; 
           [0031]      FIG. 4  is a set of reverse equations of the 3 stage interleaver for the symbol generation; and 
           [0032]      FIG. 5  is a state diagram showing the daa process. 
       
    
    
       [0033]    For purposes of clarity and brevity, like elements and components will bear the same designations and numbering throughout the Figures. 
       DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0034]      FIG. 1  is the impact of narrow band existing signal on the bit error rate (ber) as function of signal to interferer ratio (sir). 
         [0035]      FIG. 2  is the impact of narrow band existing signal on the average bit error rate (ber) as a function of average white gaussian noise (AWGN) for different levels of sir. 
         [0036]      FIG. 3  is a block diagram of the encoding process for the payload in a UWB packet. 
         [0037]      FIG. 4  is a reverse equation of the 3 stage interleave for the symbol generation. 
         [0038]      FIG. 5  is a state diagram showing the DAA process. 
         [0039]    The Detect-and-Avoid (DAA) process is based on the existing WiMedia protocol. The real time DAA operation is conducted in the host MAC, and the host MAC informs the software for the decision making process. 
         [0040]    In the  FIG. 5 , the WUSB Host is a WUSB Host Wire Adaptor (HWA). However, in general, it can be any device that performs the host or the master role in a network. A Beacon-master in UWB network or a master in the Bluetooth, or a access point device in a Pico net can be a host, and the states and the transitions in  FIG. 5  applies to all the network types regardless of the network type. The WUSB Device in  FIG. 5  is a WUSB Device Wire Adaptor (DWA). However, in general, it can be any device that performs the peripheral or the slave role in a network. A peripheral or slave device receives instructions from the host or master, and executes these instructions. 
         [0041]    The DAA operation steps are: 
         [0042]    1) The Software programs a MAC register with the Average-Packet-Drop-Rate (APDR) of the received packets from specific devices based on the AWGN study and the range check results 
         [0043]    2) The MAC requests one of these devices to send packets during a reserved DRP period for the DAA operation. The packet size, the communication channel, and the transmit power level are dictated by the requesting MAC such that any interference can directly be observed by the increasing PDR compared with the APDR when the environment contains only AWGN. The MAC conducts this operation on all channels (including the channel that the MAC is currently using for the normal operation), and stores the PDR information into the Channel-PDR register, which contains the PDR for each channel. 
         [0044]    3) The MAC also monitors the OFDM signal activities during the Clear Channel Assessment (CCA) time or during the unreserved time slot periods to decide whether the increasing PDR is due to any interference from other UWB networks. The MAC conducts this monitoring operation on all channels (including the channel that the MAC is currently using for the normal operation), and stores the information that indicates which channel has no activities into the Clear-Channel register. 
         [0045]    4) If the MAC sees UWB signals, during the CCA period, on the channel that the MAC is currently using for the normal operation, the MAC decides that the excessive PDR is due to the interference with another UWB, and reports to the upper layer controller. The upper layer controller takes one of two actions, merge its beacon with the other network, or move its network to another channel. If the controllers decided to move to another channel, it reads the Clear-Channel register and the Channel-PDR register to decide which channel is unoccupied by another UWB network and by an existing service. 
         [0046]    5) If the MAC does not detects any UWB signals in step 3, the MAC recognizes that it is causing interference to the existing service, it reports to the upper layer controller. The upper layer controller must move the network to unoccupied channel by reading the Clear-Channel and the Channel-PDR registers. 
         [0047]    In Step 1, the upper layer controller informs the MAC on the source device distance, which translates to the APDR in the AWGN environment. 
         [0048]    In Step 2, the transmit power and the packet size are determined by the distance from the source. The transmit power is set such that the receive sensitivity is comparable with the signal strength of the existing service that the MAC needs to detect. The packet size is set such that a slight increase of bit error rate, due to the interference from any existing channel, directly translates to substantial increase in the PDR. 
         [0049]    In Step 3 and Step 4, the MAC actively seeks interference with 2 methods. The MAC checks to see if the channel is occupied by other UWB signals with the CCA command. The MAC also draws a decision about the presence of an existing service by monitoring the change of the PDR. 
         [0050]      FIG. 1  and  FIG. 2  show the change of BER vs. the signal strength of the existing service (noted as the Interferer in these figures). The software uses this information and the data patterns of the specific packets to identify the sub-carrier that are also occupied by the existing services. The software may simultaneously identify a number of the existing services by changing the number of these specific packets along with the data pattern of each packet. 
         [0051]      FIG. 1  shows the impact of a narrowband signal on the UWB signal Bit Error Rate (BER) vs. the Signal to Interference ratio (SIR) with average-signal-to-AWGN (E/N)=4 db. The error rate is computed with sweeping the position of the narrowband signal from one sub-carrier to the next sub-carrier. As expected, when the narrowband signal completely occupies one sub-carrier, the error rate more than doubles the error rate when the narrowband occupies part of each sub-carrier. 
         [0052]    The set up for this analysis is for CM 1  (short range line-of-sight channel), and the SIR ratio is the average over all the sub-carriers. For example, in 384 sub-carriers case with one interferer that is directly impacting just one sub-carrier, the SIR of the impacted sub-carrier would be; 
         [0053]    10*log(384)=˜26 dB lower than the average SIR since the interferences on all other sub-carriers are zero). 
         [0054]    E is the average signal strength, and Rc is the effective code rate after puncturing and repetition. 
         [0055]      FIG. 2  shows the average BER vs. E/N for various SIR with one non-faded interferer. 
         [0056]      FIG. 3  shows the block diagram of the encoding process for the scrambled PSDU 
         [0057]    In step 2, the software also can request one of the specific devices to send a packet with payload patterns to help isolated the sub-carriers that are impacted by the existing services. In this case, the software may pre-program the packet with the payload that may not contain any meaningful information, but it would help the receiver to directly observe interference. These type of packets would provide enough information to the software for identifying the sub-carriers that are impacted by the existing services. 
         [0058]      FIG. 4  shows the mathematical equations that represent the reverse encoding process in  FIG. 3 . These equations in  FIG. 4  may be used to construct the payload patterns that would help to the software to isolate the sub-carriers that are also occupied by the existing services. 
         [0059]      FIG. 5  shows the state diagram of an implementation example of this invention. 
         [0060]    For the DAA operation, this invention may need a transmit control packet that the host would need to send out to the target device to control the transmit parameters. For the WUSB case, the protocol already includes a general transmit control packet 
         [0061]    The WUSB Host controller (software) initiates ( 502 ) the range check to all WUSB Devices, and stores this information into the MAC along with the Average Packet Drop Rate (ADPR). The APDR table contains the average packet drop rate verses the packet size and the transmit power level for the given distance (or range). 
         [0062]    After the APDR information is ready, the WUSB Host MAC reserves DRP ( 503 ) for the Interference Mitigation Operation (IMO). The WUSB Host MAC, without the upper layer controller instruction, sends Interference Check Data In (ICDI) command to the WUSB Devices ( 504 ). The ICDI command is a Data In command 
         [0063]    with a specific In target device. The WUSB Device receiving the ICDI command, it sends the packet to the WUSB Host ( 505 ) with the size and the transmit power level dictated by the WUSB Host. The WUSB Device also sends these packets on the channel that the Host requested, without the “Channel Change IE  510 ”. The transmit channel, power level, and the packet size information is in the ICDI command packet payload, and the MAC recognizes this packet since the In End Point is in the WUSB Device MAC. 
         [0064]    As the WUSB Host MAC receives these ICDI in packets from the WUSB device, it compares the Packet Drop Rate (PDR) with the ADPR ( 506 ). If the PDR is similar with ADPR, the MAC does not take any action until the next IMO DRP time slot. 
         [0065]    However, the WUSB Host MAC detects excessive PDR comparing with ADPR, the WUSB Host MAC starts searching for a clear UWB channel by comparing PDR with ADPR ( 507 ). Once the clear UWB channel search is done, the UWB Host MAC informs the WUSB controller ( 508 ) about the interference problem in the current channel. The clear UWB channel search completes with either finding all available UWB channels or not finding any available UWB channel. In either case, the WUSB MAC stores this information into the 
         [0066]    When the WUSB controller receives the interference problem information ( 508 ), the controller reads the Clear-Channel and Channel-PDR registers determining if the excessive PDR is due to interference from another UWB, or due to the existing service. 
         [0067]    If the interference is from another UWB, the WUSB Host removes the interference either by merging its beacon ( 509 ) with the other UWB network, or by executing the “Channel Change” IE ( 510 ) to move to un-interfering channel if it cannot merge the beacon. After completion of the interface removing process, it repeats the IMO operation. 
         [0068]    If the interference is with another UWB, and if there is no other Clear Channel, then the WUSB Host may shut down the network activities ( 511 ) until it finds a Clear Channel. 
         [0069]    If the interference is from an existing service, the WUSB Host removes the interference by moving to another channel ( 510 ) based on the Clear-Channel information. If there is no clear channel, the WUSB Host may lower the transmit power ( 512 ) of all sub-carriers in the channel. The WUSB Host also may lower the Transmit power ( 512 ) of selected sub-carriers if it had identified the sub-carriers that are also occupied by the existing services. 
         [0070]    While the WUSB Host shut down the network activity, the designated WUSB device continuously sends the packets according to the latest ICDI command, and the WUSB Host MAC also continuously analyze the ICDI data-in packets. Once the WUSB Host MAC identifies a clear channel, it reserves that channel ( 509 ) by starting the beacon period, and notifies the WUSB Host Controller ( 510 ) for it to establish a WUSB network in that channel. After it notifies the controller, it repeats the IMO operation. 
         [0071]    Since other modifications and changes varied to fit particular operating requirements and environments will be apparent to those skilled in the art, the invention is not considered limited to the example chosen for purposes of disclosure, and covers all changes and modifications which do not constitute departures from the true spirit and scope of this invention. 
         [0072]    Having thus described the invention, what is desired to be protected by Letters Patent is presented in the subsequently appended claims.