Abstract:
Time-frequency coding in a multi-band ultra-wideband system is generally described. In this regard a hopping code agent is presented to select a frequency hopping code for encoding and decoding from a set of predetermined FHC&#39;s for communicating with other devices in a multi-band ultra-wideband (MB-UWB) network, wherein the FHC defines a sequence of two or more pulses over two or more frequencies and wherein the FHC&#39;s include a time slot that contains no transmission. Other embodiments are also disclosed and claimed.

Description:
RELATED APPLICATION 
     This patent application claims priority to provisional U.S. patent application No. 60/451,052 filed Feb. 28, 2003 and entitled “UWB Transceiver Architecture and Associated Methods,” assigned to the assignee of the present invention and herein incorporated by reference. 
    
    
     TECHNICAL FIELD 
     Embodiments of the invention generally relate to wireless communication systems and, more particularly, to time-frequency coding in a multi-band ultra-wideband system. 
     BACKGROUND 
     Ultra-wideband (UWB) signals, according to one commonly held definition, are exemplified by a signal spectrum wherein the bandwidth divided by the center frequency is roughly 0.25. The use of ultra-wideband (UWB) signals for wireless communication, in its most basic form, has been around since the beginning of wireless communications. However, today&#39;s wireless communication environment poses many challenges to the design of ultra-wideband communication systems including, for example, the lack of a worldwide standard for ultra-wideband communications, the potential interference with narrowband wireless systems, interference with other ultra-wideband applications (e.g., RADAR, etc.), and the list goes on. Those skilled in the art will appreciate that the sheer number of such design challenges has heretofore dampened research efforts and, as such, deployment of such ultra-wideband communication solutions. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the present invention is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings in which like reference numerals refer to similar elements and in which: 
         FIG. 1  is a block diagram of an example network environment suitable for implementing the hopping code agent, according to one example embodiment of the present invention; 
         FIG. 2  is a graphical illustration of time-frequency codes applied to symbols for transmission, according to disparate embodiments of the present invention; 
         FIG. 3  is a time frequency graph depicting the use of extended time frequency codes, according to one embodiment of the present invention; 
         FIG. 4  provides graphical representations of a modulated symbol as well as a time-frequency graph of such modulated symbol(s), according to one embodiment of the invention; 
         FIG. 5  is a block diagram of an example hopping code agent architecture, according to one example embodiment of the present invention; 
         FIG. 6  is a flow chart of an example method for establishing piconets using frequency hopping codes, according to one example embodiment of the invention; and 
         FIG. 7  is a block diagram of a storage medium comprising content which, when executed by an accessing communications device, causes the communication device to implement at least one aspect of an embodiment of the invention, according to one embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the invention are generally directed to time-frequency coding in a multi-band ultra-wideband system, although the invention is not limited in this regard. According to one aspect of the invention, to be described more fully below, a hopping code agent and associated methods to establish a piconet using frequency hopping codes are presented. 
     Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrase “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments. 
       FIG. 1  is a block diagram of an example network environment suitable for implementing the hoping code agent, according to one example embodiment of the invention. In accordance with the illustrated example embodiment, network environment  100  may include one or more of a stations  102 ,  108  and  112 , hopping code agent  104 , and network areas  106 ,  110  and  114  coupled as shown in  FIG. 1 . Hopping code agent  104 , as described more fully hereinafter, may well be used in electronic appliances and network environments of greater or lesser complexity than that depicted in  FIG. 1 . Also, the innovative attributes of hopping code agent  104  as described more fully hereinafter may well be embodied in any combination of hardware and software. 
     Stations  102 ,  108  and  112  may represent laptop, desktop, or handheld computing devices or any other computing devices or appliances that can access network resources through a wireless network and that host hopping code agent  104 . As used herein, a wireless network generally represents any network wherein communications do not require the use of wires or cables. Examples of wireless networks include, but are not limited to, wireless local area networks (WLAN), wireless metropolitan area networks (WMAN), wireless wide are networks (WWAN), and wireless personal area networks (WPAN). In one embodiment, the wireless network is a WPAN using ultra wideband (UWB) wireless technology. In one embodiment, though the present invention is not so limited, stations  102 ,  108  and  112  may represent The Institute of Electrical and Electronics Engineers, Inc. (IEEE) 802.15.3a (amendment to 802.15.3 standard, under development) compliant stations. 
     Network areas  106 ,  110  and  114  may represent the maximum signal ranges for stations  102 ,  108  and  112 , respectively. Though depicted as two-dimensional circles for illustration purposes, network areas  106 ,  110  and  114  may be three-dimensional and may be any shape based on obstructions, terrain, and other factors. In one embodiment, stations  102 ,  108  and  112  may be located such that each can communicate with the others, thereby creating a piconet with shared channel access. 
     Hopping code agent  104  may have an architecture as described in greater detail with reference to  FIG. 5 . Reservation agent  104  may also perform one or more methods for establishing piconets using frequency hopping codes, such as the method described in greater detail with reference to  FIG. 6 . 
     Turning briefly to  FIG. 2 , a graphical illustration of time-frequency (FH) codes applied to symbols within a frame of content for transmission is presented, according to example embodiments of the present invention. With reference to identifier  200 , an example embodiment wherein the extension factor applied to the FH code is one (1), i.e., frequency hopping is occurring on an incremental basis, e.g., on a per-chip basis as shown in graph  200 . Thus, for each chip (Tc) within a sub-frame (Tf 1 ), a new frequency band (f 1 , f 2 , f 3  . . . f 7 ) is selected for transmission. 
     In graph  250 , however, an example embodiment where an extension factor of four (4) is applied, i.e., frequency hopping is occurring after four (4) sequential chips are transmitted within a frequency band, before hopping to the next frequency band. Thus, four chips are transmitted on f 1 , then four on f 4 , and so on, as depicted. In this regard, according to one aspect of the invention, the received content is processed to transmit any number of sequential pulses (M) within at least a subset of any number (N) of narrower frequency bands of the UWB spectrum. These pulses can also be transmitted and received in parallel, as in a multi-carrier CDMA or OFDM system. 
     As shown in  FIG. 2 , the frequencies selected appear in numerical order (i.e. f 1 , then f 2 , and so on), however, it should be appreciated that the frequencies used in a frequency hopping code may occur in any sequence. In one embodiment, a set of nine discrete sequences (or codes) containing eight sub-bands out of nine available sub-bands may be utilized based on Galois Field GF(p) or Extended Galois Field GF(p m ), although the present invention is not limited to these numbers of sequences, sub-bands contained, or sub-bands available. One skilled in the art would appreciate that utilizing sets of sequences based on the theory of irreducible polynomials over GF(p m ), where p is prime, and m is an integer, may produce at most one coincidence (potential collision) between any two sequences for any offset. In another embodiment, there may be a time slot(s) in a sequence(s) that contain no transmission in order to create more available sequences based on the number of sub-bands available and/or contained in the sequences. 
       FIG. 3  is a time-frequency graph depicting the use of extended time frequency codes, according to one aspect of the invention. In accordance with the illustrated example embodiment of  FIG. 3 , graph  300  depicts a number of chips being transmit within a first narrower frequency band (f 1 ) of the UWB spectrum before hopping to the next narrower frequency band (f 2 ) for transmission. More particularly, graph  300  illustrates the block interleaving of four (4) bi-orthogonal codewords ( 1  . . .  4 ) with a 6/3 byte interleaving delay (depending on in-phase (I)/quadrature (Q) interleaving strategy). In this regard, the incremental content (chips, symbols, etc.) of a frame (denoted as  1 ,  2 ,  3  . . . ) is spread across multiple frequency bands and separated in time (e.g., 84 nanoseconds). 
       FIG. 4  provides a graphical representation of a modulated frame element (e.g., symbol), as well as a time-frequency graph of such modulated frame element, in accordance with one example embodiment of the invention. In accordance with one example embodiment of the present invention, each symbol is transmitted within the narrower frequency band (f 1 , f 2  . . . f N ) using a rectified cosine waveform  400 , although the invention is not limited in this respect. According to one example implementation, a three (3) nanosecond pulse with a rectified cosine shape is generated with a 700 MHz bandwidth, and 550 MHz channel separation. According to one example implementation, to reduce the effect of interference (e.g., narrowband interference) and/or channel overlap, a frequency separation offset of 275 MHz may be selectively applied. The transmission of symbols using a FH codes is presented with reference to graph  450 . 
       FIG. 5  is a block diagram of an example hopping code agent architecture, according to one example embodiment of the invention. As shown, hopping code agent  104  may include one or more of control logic  502 , memory  504 , wireless network interface  506 , and hopping code engine  508  coupled as shown in  FIG. 5 . In accordance with one aspect of the present invention, to be developed more fully below, hopping code agent  104  may include a hopping code engine  508  comprising one or more of select services  510 , encode services  512 , and/or decode services  514 . It is to be appreciated that, although depicted as a number of disparate functional blocks, one or more of elements  502 - 514  may well be combined into one or more multi-functional blocks. Similarly, hopping code engine  508  may well be practiced with fewer functional blocks, i.e., with only encode services  512 , without deviating from the spirit and scope of the present invention, and may well be implemented in hardware, software, firmware, or any combination thereof. In this regard, hopping code agent  104  in general, and hopping code engine  508  in particular, are merely illustrative of one example implementation of one aspect of the present invention. As used herein, hopping code agent  104  may well be embodied in hardware, software, firmware and/or any combination thereof. 
     As introduced above, hopping code agent  104  may have the ability to establish a piconet using frequency hopping codes. In one embodiment, an access point establishes a frequency hopping code with hopping code agent  104  to be used in communications with stations attempting to associate with the access point. In another embodiment, hopping code agent  104  may allow a station attempting to locate and associate with another station (i.e., an access point) to determine the established frequency hopping code. One skilled in the art would appreciate that hopping code agent  104  can provide for efficient use of bandwidth by minimizing collisions with communications of the piconet. 
     As used herein control logic  502  provides the logical interface between hopping code agent  104  and its host station (for example  102 ). In this regard, control logic  502  may manage one or more aspects of hopping code agent  104  to provide a communication interface from station  102  to wireless network communications, e.g., through wireless interface  506  and one or more antenna(e). 
     According to one aspect of the present invention, though the claims are not so limited, control logic  502  may receive event indications such as, e.g., receipt from the host station of a communication to be transmitted. Upon receiving such an indication, control logic  502  may selectively invoke the resource(s) of hopping code engine  508 . As part of an example method for establishing piconets using frequency hopping codes, as explained in greater detail with reference to  FIG. 6 , control logic  502  may selectively invoke select services  510  that may a frequency hopping code to be utilized as part of a piconet. Control logic  502  also may selectively invoke encode services  512  or decode services  514 , as explained in greater detail with reference to  FIG. 6 , to encode communication(s) to transmit or decode communication(s) received, respectively. As used herein, control, logic  502  is intended to represent any of a wide variety of control logic known in the art and, as such, may well be implemented as a microprocessor, a micro-controller, a field-programmable gate array (FPGA), application specific integrated circuit (ASIC), programmable logic device (PLD) and the like. In some implementations, control logic  502  is intended to represent content (e.g., software instructions, etc.), which when executed implements the features of control logic  502  described herein. 
     Memory  504  is intended to represent any of a wide variety of memory devices and/or systems known in the art. According to one example implementation, though the claims are not so limited, memory  504  may well include volatile and non-volatile memory elements, possibly random access memory (RAM) and/or read only memory (ROM). Memory  504  may be used to store communication(s) to be encoded/decoded and/or a frequency hopping code(s) to be used for encoding/decoding. 
     Wireless network interface  506  provides a path through which hopping code agent  104  can communicate with other network devices, for example among stations  102 ,  108  and  112 . Wireless network interface  506  is intended to represent any of a wide variety of network interfaces and/or controllers known in the art. In one embodiment, wireless network interface includes a transmitter and receiver as described in U.S. patent application Ser. No. 10/379,395 filed Mar. 3, 2003 and entitled “AN ULTRA-WIDEBAND TRANSCEIVER ARCHITECTURE AND ASSOCIATED METHODS,” assigned to the assignee of the present invention and herein incorporated by reference. 
     As introduced above, hopping code engine  508  may be selectively invoked by control logic  502  to select a frequency hopping code, to encode communication(s) to be transmitted with the frequency hopping code, or to decode communication(s) received with the frequency hopping code. In accordance with the illustrated example implementation of  FIG. 5 , hopping code engine  508  is depicted comprising one or more of select services  510 , encode services  512  and decode services  514 . Although depicted as a number of disparate elements, those skilled in the art will appreciate that one or more elements  510 - 514  of hopping code engine  508  may well be combined without deviating from the scope and spirit of the present invention. 
     Select services  510 , as introduced above, may provide hopping code agent  104  with the ability to select a frequency hopping code. In one example embodiment, select services  510  may select a frequency hopping code by attempting to decode communication(s) using one of a plurality of frequency hopping codes. If a beacon signal is decoded, then select services  510  may select the frequency hopping code used to decode the beacon signal. If a beacon signal is not decoded, select services  510  may attempt decoding using a different frequency hopping code until a beacon signal is decoded. In another example embodiment, select services  510  may scan available frequencies for activity, and then selects a frequency hopping code that may avoid the most likely sources of interference (for example, the most active frequencies). In another example embodiment, select services  510  may employ a method described in the aforementioned patent application entitled “AN ULTRA-WIDEBAND TRANSCEIVER ARCHITECTURE AND ASSOCIATED METHODS,” assigned to the assignee of the present invention and herein incorporated by reference. 
     As introduced above, encode services  512  may provide hopping code agent  104  with the ability to encode communication(s) to be transmitted using the selected frequency hopping code. In one example embodiment, encode services  512  may employ a method described in the aforementioned patent application entitled “AN ULTRA-WIDEBAND TRANSCEIVER ARCHITECTURE AND ASSOCIATED METHODS,” assigned to the assignee of the present invention and herein incorporated by reference. 
     Decode services  514 , as introduced above, may provide hopping code agent  104  with the ability to decode communication(s) received using the selected frequency hopping code. In one embodiment, decode services  514  may employ a method described in the aforementioned patent application entitled “AN ULTRA-WIDEBAND TRANSCEIVER ARCHITECTURE AND ASSOCIATED METHODS,” assigned to the assignee of the present invention and herein incorporated by reference. 
     Turning next to  FIG. 6 , a network control function performed by hopping code agent  104  introduced above will be described. More particularly, in accordance with another aspect of an embodiment of the invention,  FIG. 6  illustrates a flow chart of an example method for establishing piconets using frequency hopping codes, according to one example embodiment of the invention. It will be readily apparent to those of ordinary skill in the art that although the following operations may be described as a sequential process, many of the operations may in fact be performed in parallel or concurrently. In addition, the order of the operations may be re-arranged without departing from the spirit of embodiments of the invention. 
     According to but one example implementation, the method of  FIG. 6  begins with control logic  502  invoking select services  510  to select ( 602 ) a frequency hopping code. In one example embodiment, select services  510  of station  102  may select a frequency hopping code that may minimize interference with other active frequencies and use the selected frequency hopping code to encode and transmit a beacon signal through wireless network interface  506  to stations  108  and  112 . In one example embodiment, stations  108  and  112  determine the frequency hopping code to be used in the piconet by determining which frequency hopping code from a set of frequency hopping codes decodes the beacon signal from station  102 . 
     Next, encode services  512  may be invoked to encode ( 604 ) communication(s). In one example embodiment, transmit services  512  of station  102  may broadcast (and rebroadcast if necessary) frames to station  108  and/or station  112  that are encoded using the selected frequency hopping code. 
     Control logic  502  may then decode ( 606 ) the communication(s) by invoking decode services  514 . In one example embodiment, station  108  and/or station  112  decode (using the selected frequency hopping code) encoded frames that were broadcast by station  102 . 
     It will be appreciated by those skilled in the art that the foregoing was but a mere illustration of the teachings of the present invention, as other embodiments and implementations are anticipated within the scope of the invention. Examples of such alternate embodiments are briefly described below. 
       FIG. 7  is a block diagram of an example storage medium comprising content which, when executed by an accessing appliance, may cause the appliance to implement one or more aspects of an embodiment of the invention. In this regard, storage medium  700  includes content  702  to implement one or more aspects of hopping code agent  104 , described above. 
     As used herein, the machine-readable medium  700  may include, but is not limited to, floppy diskettes, optical disks, CD-ROMs, and magneto-optical disks, ROMs, RAMs, EPROMs, EEPROMs, magnet or optical cards, flash memory, or other type of media/machine-readable medium suitable for storing electronic instructions. Moreover, the present invention may also be downloaded as a computer program product, wherein the program may be transferred from a remote computer to a requesting computer by way of data signals embodied in a carrier wave or other propagation medium via a communication link (e.g., a wired/wireless modem or network connection). 
     In the description above, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without some of these specific details. In other instances, well-known structures and devices are shown in block diagram form. 
     The present invention includes various steps. The steps of the present invention may be performed by hardware components, or may be embodied in machine-executable content (e.g., instructions), which may be used to cause a general-purpose or special-purpose processor or logic circuits programmed with the instructions to perform the steps. Alternatively, the steps may be performed by a combination of hardware and software. Moreover, although the invention has been described in the context of a network device, those skilled in the art will appreciate that such functionality may well be embodied in any of number of alternate embodiments such as, for example, integrated within a computing device (e.g., a server). 
     Many of the methods are described in their most basic form but steps can be added to or deleted from any of the methods and information can be added or subtracted from any of the described messages without departing from the basic scope of the present invention. Any number of variations of the inventive concept are anticipated within the scope and spirit of the present invention. 
     In this regard, the particular illustrated example embodiments are not provided to limit the invention but merely to illustrate it. Thus, the scope of the present invention is not to be determined by the specific examples provided above but only by the plain language of the following claims.