Abstract:
Systems for supporting multi-channel dynamically controlled diversity reception in wireless communications include a plurality M of receivers coupled to M antennas and configured to handle N communication channels wherein N≦M≦(2*N−1) and N channel state machines configured to dynamically allocate multiple channels of the N channels to the M receivers to support dynamic switched diversity for multi-channel dynamically controlled reception. Each channel state machine is configured to control the operation of each receiver. Arbitration is performed between channel state machines when such channel state machines work concurrently. In some embodiments, a lock state machine inside each channel state machine accelerates the locking time of a receiver based on at least one parameter received from another receiver.

Description:
CROSS REFERENCE TO EXISTING APPLICATIONS 
       [0001]    This application is related to and claims priority from U.S. Provisional Patent Application No. 61/977,237 titled “Method and system for supporting dual-channel and diversity using two receivers” and filed Apr. 9, 2014, which is incorporated herein by reference in its entirety. 
     
    
     FIELD 
       [0002]    Embodiments of the invention relate in general to wireless communication systems and methods, and in particular to systems and methods for dynamically controlled diversity reception of a plurality of different channels allocated dynamically to receivers. 
       BACKGROUND 
       [0003]    Some wireless communication standards have a spectrum allocation of multiple wireless channels (frequency bands), where each channel has a distinct functionality and where several channels need to be processed concurrently. The channels are completely independent, receiving packets from different sources at different times. For example, the vehicle-to-vehicle (V2V) communication IEEE standard has seven allocated channels, of which one is allocated for safety and others for services. Concurrent reception of both the safety channel and of a service channel is required. 
         [0004]    Antenna diversity is a well-known method to improve the communication quality. Some implementations combine the signals from all antennas for maximal reception quality. This approach is called “full diversity”. Other implementations use only a subset of the antennas, since the number of processing elements denoted as “receivers” is lower than the number of antennas. The field of “switching diversity” or “switched diversity” involves studies of preferred antenna selection methods. A full diversity solution is more expensive than a switching diversity solution, because the size and complexity of full diversity implementation are higher. However, full diversity provides better communication quality. 
         [0005]    The switching diversity theory is focused on receiving a single source of data (single channel) at a time. However, in some communication environments such as V2V, independent data links are handled concurrently in different channels. Each channel uses a different frequency. 
         [0006]    Some V2V communication installations (or “systems”) mandate the use of two antennas for omni-directional antenna pattern. For full diversity implementation of two channels, the number of receivers has to be twice the number of channels, as two receivers have a fixed allocation to one channel. For example, a vehicle can use a single antenna if the antenna is positioned on the top of its roof. Other vehicles, like vehicles without observable antennas, need two antennas positioned either on windows, bumpers or side-mirrors. 
         [0007]    The term “dynamic control” with reference to receivers is known. Dynamically controlled diversity receivers are capable of performing various diversity receiving and processing schemes, however involving only one channel. The term “dynamic control” with reference to a receiver also refers to the configuration and capability of a receiver to select one or two antennas for reception of a single channel. 
         [0008]      FIG. 1A  illustrates a known wireless communication system  100  that supports reception of two channels with full antenna diversity. System  100  includes exemplarily two antennas A and B that serve two channels. Each antenna covers a partial antenna. Together, the two antennas provide omnidirectional pattern. A splitter and combiner “block” per antenna (respectively blocks  102  and  104 ) is needed to operate two different channels with a single antenna. The splitter and combiner block is used to reduce the number of antennas. For example, blocks  102  and  104  could be dispensed with if four antennas were implemented and each antenna was routed directly to a receiver. Four receivers  106 ,  108 ,  110  and  112  are needed for implementation of full availability of this scheme. System  100  further includes two “full diversity” receivers  114  and  116 , each receiving two antennas and performing full diversity reception. Each receiver outputs a respective channel, respectively channels  1  and  2 . Such a system is feasible but expensive and requires a large physical size. 
         [0009]      FIG. 1B  illustrates a known wireless communication system  100 ′ that supports reception of two channels with switched antenna diversity. System  100 ′ is similar to system  100  but includes two diversity switches  122  and  124  coupled respectively to two “regular” receivers  126  and  128  instead of the two full diversity receivers  114  and  116 . Each diversity switch receives two antennas and selects one antenna for processing at the respective receiver. Each receiver processes a single antenna and outputs a single channel (respectively channels  1  and  2 ) but does not provide receiver gain. The switching control is described in known switched diversity art. Such a system is feasible but shows limited performance where diversity gain is needed. 
         [0010]    There is therefore a need for, and it would be highly desirable to have systems and related methods that handle multiple channels with dynamically controlled diversity reception, i.e. with a number of receivers that is smaller than twice the number of channels, to reduce system cost and size. 
       SUMMARY 
       [0011]    Embodiments disclosed herein relate to wireless communication systems that handle multiple data streams (multiple channels) with dynamically controlled diversity reception, i.e. with a number of receivers smaller than twice the number of channels. Each receiver is associated with a receiver chain (not shown). Hereinafter, “receiver” and “receiver chain” (or simply “chain”) may be used interchangeably. Dynamically controlled reception as disclosed herein, in which the number of receivers is smaller than twice the number of channels, is termed “multi-channel dynamically controlled diversity reception” or “multi-channel multi-receiver dynamically controlled diversity reception”. In various embodiments, some of which are described in detail hereinbelow, multi-channel dynamically controlled diversity reception is applied to multiple channels by using (or performing) dynamic multiple channel allocation. 
         [0012]    In some multi-channel dynamically controlled diversity reception system and method embodiments disclosed herein, the number of receivers can be equal to the number of channels, providing a system with minimal antenna count but with some compromised availability. In some embodiments, the number of receivers is larger than the number of channels but smaller than twice the number of channels. While described in detail with reference to two antennas, systems and methods disclosed herein can be generalized to support more antennas, for example three antennas. 
         [0013]    In an embodiment there is provided a system for wireless communication, comprising a plurality M of receivers coupled to M antennas and configured to handle N communication channels wherein N≦M≦(2*N−1) and N channel state machines configured to dynamically allocate multiple channels of the N channels to the M receivers to support dynamic switched diversity for multi-channel dynamically controlled reception. In an embodiment, a system further includes an arbitration component configured to arbitrate between channel state machines when such channel state machines work concurrently. The arbitration may include allocation of a different time slot to each channel state machine or includes allocation of an available receiver per priority of a processed channel. In an embodiment, each channel state machine is configured to control the operation of each receiver. In an embodiment, each receiver is dynamically configured to process a single channel. In an embodiment, a system further includes a fast lock control mechanism operative to accelerate the locking time of one receiver based on at least one parameter received from another receiver. The fast lock mechanism may include, for each channel state machine, a lock state machine configured to receive an input parameter and a copy command parameter from another lock state machine. The input parameter may be an initial receiver gain, a frequency shift or a combination of the two. The copy command parameter may include a set gain command, a frequency shift command and a combination of the two. 
         [0014]    In an embodiment there is provided a method for wireless communication, comprising steps of providing a plurality M of receivers coupled to M antennas and configured to handle N communication channels wherein N≦M≦(2*N−1), and dynamically allocating the N channels to the M receivers while considering channel priority, thereby supporting dynamic switched diversity for multi-channel dynamically controlled reception. The step of dynamically allocating may include configuring N channel state machines to perform dynamic allocation of multiple channels to receivers and dynamically configuring each receiver to process a single channel. The dynamic configuring may include accelerating the locking time of one receiver based on at least one parameter received from another receiver. The acceleration is performed by a lock state machine included in each channel state machine, each lock state machine configured to receive an input parameter and a copy command parameter from another lock state machine. 
         [0015]    In an embodiment, a method further includes the step of arbitrating between channel state machines when such channel state machines work concurrently. The arbitration may include allocating a different time slot to each channel state machine, or allocating an available receiver per priority of a processed channel. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    Non-limiting embodiments are herein described, by way of example only, with reference to the accompanying drawings, wherein: 
           [0017]      FIG. 1A  illustrates a known wireless communication system that supports reception of two channels with antenna full diversity; 
           [0018]      FIG. 1B  illustrates a known wireless communication system that supports reception of two channels with antenna switching diversity; 
           [0019]      FIG. 2A  illustrates an embodiment of a wireless communication system that supports two-channel two-receiver dynamically controlled diversity reception; 
           [0020]      FIG. 2B  illustrates an embodiment of a wireless communication system that supports three-channel three-receiver so dynamically controlled diversity reception; 
           [0021]      FIG. 3  illustrates an embodiment of a generalized wireless communication that supports multi-channel dynamically controlled diversity reception; 
           [0022]      FIG. 4  illustrates the operation of the fast lock control component in  FIG. 3 ; 
           [0023]      FIG. 5  shows a state flow diagram implemented per channel. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]      FIG. 2A  illustrates an embodiment numbered  200  of a wireless communication system that supports two-channel two-receiver dynamically controlled diversity reception. System  200  includes two antennas, a first antenna A and a second antenna B coupled through respective receivers and inputs  202  and  204  to a dual-channel dynamically controlled receiver  206  that includes two receivers, a receiver  208  and a receiver  210 . In system  200 , the number of receivers is equal to the number of channels. Each antenna has a fixed route to dual-channel dynamically controlled receiver  206 , but since receiver  206  can be dynamically allocated to each channel, each antenna can serve both channels. The system outputs channels  1  and  2 , where the output is taken from the receiver currently allocated for the channel. This means that output channel  1  can result from receiver  208 , receiver  210  or a combination of both receivers. Similarly, output channel  2  can result from receiver  208 , receiver  210  or a combination of both receivers. The cost is halved relative to that of system  100  in  FIG. 1A . The complexity of RF design is lower, due to the elimination of splitter and combiner blocks  102  and  104  of system  100 . 
         [0025]    An additional advantage of system  200  is the ability of each receiver  208  and  210  to be dynamically allocated to a different channel, and the combination of this ability with multi-channel dynamically controlled diversity reception, a combination that decides which antenna(s) will be used for reception. 
         [0026]    In use, in an idle state when no packet is received, the two channels are monitored continuously, each by a different receiver (routed to a fixed antenna). When a packet start is detected under certain conditions (e.g. once measured packet energy crosses a threshold and signal properties are validated), one receiver receives the channel in which the packet start is detected. The other receiver is then dynamically allocated to the channel by switching to receive the channel. That is, both receivers process the preamble of the same packet. If antenna diversity provides a noticeable reception processing gain (e.g. an improvement from, for example, a 40% expected packet error to 10% expected packet error), more specifically if the measured packet energies at both antennas are similar, and if the probability of receiving a packet at a single antenna without diversity is below a preset target (exemplarily 1% or 10%), both receivers will keep receiving the same channel in diversity mode. Otherwise, the receiver with the higher measured packet energy chain will receive the packet, while the other receiver will return to monitor the other channel. 
         [0027]    System  200  and its method of use ensure that availability to receive a packet from any source is as high as possible, and that diversity gain is provided when needed and possible. The scheme can allocate different importance priority to each channel and set a different availability target for each channel by allocating priorities to an arbitration component ( 306  in  FIG. 3 ). For example, in V2V communication, one channel is used for safety, which should have perfect or near perfect availability, while the other channels are used for services, where availability can be compromised. 
         [0028]      FIG. 2B  illustrates an embodiment numbered  200 ′ of a wireless communication system that supports three-channel three-receiver dynamically controlled diversity reception. The system illustrated in  FIG. 2B  has a higher number of receivers than the number of channels but a lower number of receivers than twice the number of channels. Like system  200 , system  200 ′ includes a first antenna A and a second antenna B. These antennas are coupled through three receivers  220 ,  222  and  224  to a three-channel dynamically controlled receiver  206 ′ having 3 receivers  226 ,  228  and  230 . Receivers  220  and  222  are routed directly to antenna A via a splitter/combiner block  232 . Receiver  224  is routed directly to antenna B. In use, both channels monitor continuously antenna A. Antenna B serves one channel based on need. Three-channel dynamically controlled receiver  206 ′ thus supports concurrent operation of 3 receivers. While receiver  206 ′ is potentially more expensive than receiver  206 , it provides full availability. Like system  200 , system  200 ′ provides dynamic allocation of receivers to channels and applies multi-channel dynamically controlled reception. The only difference lies in the added receiver resources in system  200 ′. 
         [0029]      FIG. 3  illustrates an embodiment numbered  300  of a generalized wireless communication system with multi-channel dynamically controlled diversity reception. System  300  includes M receivers  302   1-M  for processing N channels. M may vary between N and 2*N−1, where N is 2 or larger. It should be understood that the M receivers coupled to the N-channels provide a “N-channel M-receiver dynamically controlled receiver” (not shown). Each receiver can process a single channel, selected dynamically. Each receiver (and receiver) works in parallel with all other receivers. System  300  further includes N state machines marked  304   1-N  for controlling the operation of each channel. Each state machine can control each receiver, determining the channel for processing and having indication about its activity and about the priority of the currently handled channel. In other words, the channel state machines perform dynamic allocation of receivers. System  300  further includes an arbitration component  306  that coordinates between the various state machines that work concurrently. Arbitration component  306  may be a hardware (HW) component or a software (SW) module. Arbitration component  306  may exemplarily implement arbitration schemes: 1) by allocating a different time slot to each channel state machine to ensure that at each given moment only one channel state machine can make decisions, or 2) by allocating available receiver per priority of processed channel and/or per need. System  300  further includes optionally a fast lock control mechanism  308  (typically HW, but also implementable as a SW module) that implements fast lock functionality of a receiver  302 . The entire locking process needs to converge in a very short time, during packet preamble. System  300  further includes a diversity combiner  310  for exchanging dynamically information between two or more receivers in order to provide diversity gain. The diversity combiner allows the receivers handling the same channel to process the channel collectively. 
         [0030]      FIG. 4  provides details of the fast lock control mechanism  308  in  FIG. 3 . A lock state machine  402  (which is a subset of a channel state machine  304  in  FIG. 3 ) of a receiver is modified vs. a known art lock state machine to receive two inputs: an input parameter  404  and a copy command parameter  406 . This means that the lock state machine dynamically changes from one receiver to another while adopting parameters existing in another lock state machine. This is in contrast with known lock state machines, which have no input. Such known lock state machines base their decision solely on the received signal. In known systems, there is no ability to exchange information between different lock state machines in order to accelerate locking of a lock state machine based on the temporal parameters of another state machine. When a command  406  to copy a parameter from a first receiver to a second receiver is issued by a channel state machine  304  after deciding to use the second receiver to process the channel, input parameter  404  and copy command parameter  406  are loaded to the lock state machine of the respective channel state machine and are used. Exemplarily, input parameter  404  may include an initial receiver gain and/or a frequency shift of the second receiver to minimize the time needed for measuring both the initial receiver gain and the frequency shift of the second receiver. An exemplary command may be “set gain to XX dB (where XX is for example 66 dB) and “apply a frequency shift of YY KHz” (where YY is for example 100 KHz). The parameters (input  404  and copy command  406 ) of the lock state machine are output at a parameters output interface  408 , for use (if needed) by other receivers. 
         [0031]      FIG. 5  shows a state flow diagram implemented per channel. N parallel instances of the state machine exist and work concurrently. This generic flow applies to any values of N and M. A particular state machine waits in an initial state  500  for packet start. The state machine relates to a single channel and can control two (first and second) receivers. A receiver may be available or unavailable. The receiver availability state may consider several properties: 
         [0000]    a) Receiver activity: if the receiver is active then using it will interfere to the currently received packet. In that case, decision to use the receiver should be more cautious. If receiver is inactive, then nothing prevents from using it.
 
b) Measured packet energy: if the preliminary energy measurement is high, then there is no need to utilize the second receiver since the packet will be received anyhow.
 
c) Channel priority: if the first receiver is active and if the processed channel has lower priority, then the channel can be interrupted. If the processed channel has higher priority, then it cannot be interrupted.
 
d) Wireless properties: typically, wireless properties are unknown at packet start. However, if wireless properties information like delay spread or non-line-of-sight is available, then this information can be considered as well and may impact the decision. Complex wireless reception requires higher energy and will likely benefit more from diversity.
 
         [0032]    Once a packet start is detected, the flow leaves state  500 . If a second receiver is unavailable, then the flow jumps to state  506 , where a packet is received using a single antenna, i.e. the same antenna used for packet detection. The flow stops following packet end and the state machine returns to wait for a new packet start in state  500 . If a second receiver is available when the state machine waits in initial state  500  and once a packet start is detected, the flow jumps to state  502 . In state  502 , the packet energy is measured by the second receiver and a decision to apply diversity or to receive using only a single antenna is based on the measured energy (for example, if the energy difference between energies measured at the two antennas is within a small value, for example 3 dB). If diversity is needed, then state  504  becomes active. If diversity is not needed, then state  506  becomes active. The receiver selected for reception is the one with the higher energy among the two. From both states  504  and  506 , the flow returns to state  500  once packet transmission ends. From state  504 , the flow can jump to state  506  if diversity was interrupted by another state machine with higher priority. 
         [0033]    The decision of diversity activation after state  502  considers the energy difference between the two receivers: diversity provides gain only when the packet has similar energy (e.g. within about 3 dB) in both receivers. If the difference the energy measured in the two different receivers is too high (e.g. about 3 dB) then there is no need to activate diversity. One advantage of the flow above is the ability to implement dynamic allocation of a lock state machine and ability to adopt parameters from another lock state machine. 
         [0034]    The state flow shown in  FIG. 5  can operate with different considerations. For example, considerations after state  500  can be checked only after state  502 . That is, checks such as a check if a receiver is available or unavailable or the consideration of properties mentioned above can be deferred to state  502  instead of being checked in state  500 . 
       EXAMPLES OF OPERATION 
     Example 1 
       [0035]    This example (related to  FIG. 2A ) involves a configuration of two channels and two receivers. Channel  1  has higher priority than channel  2 . Receiver  1  monitors channel  1 . Receiver  2  monitors channel  2 . A packet is detected at channel  2 . Regardless of any signal property, the lower priority of channel  2  indicates that only receiver  2  will be allocated for its reception, even if the packet energy is low. The current status is that receiver  1  monitors channel  1  and receiver  2  receives channel  2 . 
         [0036]    In continuation, a packet start is monitored for channel  1 . The energy is low, and since channel  1  has higher priority, reception of channel  2  is interrupted and receiver  2  is now allocated for channel  1 . The packet energy at receiver  2  is higher than measured at receiver  1 , meaning that channel  1  can be received only from receiver  2 . Receiver  1  becomes available, and is allocated for monitoring channel  2 . The current status is that receiver  2  receives channel  1  and receiver  1  monitors channel  2 . Thus, the packet received in channel  2  is lost. 
       Example 2 
       [0037]    This example (related to  FIG. 2B ) involves a configuration of two channels and three receivers (with three receivers). Channel  1  has higher priority than channel  2 . Receiver  1  monitors channel  1  and receiver  2  monitors channel  2 . A packet is detected at channel  2 . The packet energy is low, and since receiver  3  is available, it switches to channel  2  and measures the packet energy. The switching is done by a frequency change command and by applying the fast lock mechanism. The measured packet energy is similar to the packet energy measured at receiver  2 , and therefore diversity reception is activated. The current status is that receiver  1  monitors channel  1 , and receivers  2  and  3  is receive channel  2 . 
         [0038]    In continuation, a packet start is monitored for channel  1 . The energy is low, and since channel  1  has higher priority, the diversity of channel  2  is interrupted and receiver  3  is now allocated to channel  1 . The packet energy of receiver  3  is higher than that measured at receiver  1 , and channel  1  is received only from receiver  3 . The current status is that receiver  3  receives channel  1  and receiver  2  receives channel  2 . 
         [0039]    While this disclosure has been described in terms of certain embodiments and generally associated methods, alterations and permutations of the embodiments and methods will be apparent to those skilled in the art. The disclosure is to be understood as not limited by the specific embodiments described herein, but only by the scope of the appended claims.