Patent Publication Number: US-8126492-B2

Title: Vehicle communications system

Description:
RELATED APPLICATIONS 
     This application claims the benefit of provisional application 61/099,982 filed Sep. 25, 2008 by the same inventors. 
    
    
     FIELD OF THE INVENTION 
     The present invention generally relates to a system for providing wireless communications between members of a vehicle crew, both inside the vehicle and outside the vehicle within 1000 feet of a particular point on the vehicle. Particular embodiments of the invention relate to emergency response vehicles, such as fire trucks and ambulances. 
     BACKGROUND OF THE INVENTION 
     Wired intercoms for communicating between crew members of vehicles are well known. U.S. Pat. No. 6,223,062 B1 for a COMMUNICATIONS INTERFACE ADAPTER issued to Davidson et al. on Apr. 24, 2001, discloses an interface between a vehicle intercom and a radio transceiver that allows a crew member who has disconnected from the wired intercom to access the wired intercom from outside the vehicle via radio transceiver through the communications interface adapter to the intercom. 
     While wired communications devices are less susceptible to interference, wireless communications enable greater freedom of action. 
     Accordingly, it is desirable to provide an improved vehicle crew communication system that is entirely wireless, resistant to interference, allows a plurality of disembarked crew members to communicate over the intercom at operationally useful distances, allows wireless communication within the vehicle, and avoids aggregating adapters to legacy systems. It is further desirable to have a vehicle crew communication system that permits intercom headset access to one or more radios for longer range communications. 
     BRIEF SUMMARY OF THE INVENTION 
     A system is provided for providing interference-resistant wireless communications for a vehicle crew both embarked in and disembarked from the vehicle. The system provides a five-channel base station (corresponding to five allocated channels in the 1.9 GHz band) able to communicate with up to 60 headsets by virtue of the twelve TDMA full-duplex slots in each channel. The bandwidth is sufficient to allow for digital encryption, thereby reducing the likelihood of interception during use in national security applications. Channel selection is performed automatically, using the DECT 6.0 protocol (or follow-on) in the US or DECT in Europe, so hand selection of channels, and errors made in that process, are avoided. Likewise, resistance to interference is enhanced by the use of DECT 6.0 (or follow-on) and DECT protocols. The combination of the communications system and the vehicle is within the scope of the invention. 
     An improved vehicle crew communications system including: a vehicle capable of carrying a crew, such crew including a plurality of human crew members who are users of the system; a base station coupled to the vehicle; an intercom communicatively coupled to the base station via a microphone input in the intercom and also communicatively coupled to a radio; a wireless headset wirelessly communicatively coupled via a wireless TDMA link to a particular base station; wherein the improvements comprise: increase in the number of the wireless headsets usable at once with one base station; increase in the distance from the vehicle at which a wireless headset is operable; full duplex communication over digitally encrypted DECT protocol links from one the base station; pairing of each particular headset of a wireless headset to a particular base station of a base station; wireless communications within and exterior to the vehicle; automatic slot and channel selection to avoid interference, wherein the selection is transparent to the users; removal of the need to manually select the channel for a wireless headset; and a noise-cancelling microphone with noise threshold, noise attenuation, and line echo cancellation tuned to parameters of the intercom. 
     The improved vehicle crew communications system, wherein a base station includes five or less base stations. The improved vehicle crew communications system, wherein a wireless headset includes four or less wireless headsets per base station. The improved vehicle crew communications system, wherein each base station of a base station provides five channels each having: twelve full-duplex TDMA links; a DECT protocol in the 1920-1930 MHz sub-band; a firmware digital signal processing algorithm for reducing line echo; and encryption. The improved vehicle crew communications system, wherein a particular wireless headset includes: a head-engaging web; a noise-canceling microphone coupled to the web; a microphone circuit coupled to the microphone, wherein the microphone circuit employs noise-gating; noise-reduction ear covers coupled to the web; a volume control switch; and a push-to-talk (PTT) switch. The improved vehicle crew communications system, wherein the microphone is automatically constantly on and the PTT switch provides access to a radio when the PTT switch is activated. The improved vehicle crew communications system, wherein the microphone is not automatically constantly on and the PTT is operable to switch the microphone to constantly on. The improved vehicle crew communications system, wherein the microphone is never constantly on and the PTT switch includes an off-biased button PTT switch operable to turn on the microphone only while the off-biased button PTT switch is depressed. The improved vehicle crew communications system, wherein the microphone circuit employs noise gating tuned to the microphone input of the intercom and further provides balancing of an audio level to allow the user&#39;s voice to break over the noise gate. The improved vehicle crew communications system, wherein the base station includes firmware including an adaptive digital signal processing algorithm to reduce side tone from a wireless headset. The improved vehicle crew communications system, wherein a wireless headset includes a rechargeable headset battery, the system further including a battery charger coupled to the vehicle for charging a rechargeable battery. The improved vehicle crew communications system, wherein a wireless headset includes a rechargeable headset, the system further including a charger coupled to the vehicle for charging a rechargeable headset. 
     An improved vehicle crew communications system including: a vehicle capable of carrying a crew, such crew including a plurality of human crew members who are users of the system; a base station coupled to the vehicle wherein each base station of a base station provides five channels each having: twelve full-duplex TDMA links; a DECT protocol in the 1920-1930 MHz sub-band; a firmware digital signal processing algorithm for reducing line echo; and encryption; an intercom communicatively coupled to a base station via a microphone input in the intercom and also communicatively coupled to a radio; a wireless headset wirelessly communicatively coupled via a TDMA link to a particular base station; wherein the improvements comprise: increase in number of wireless headsets usable at once with one base station; increase in a distance from the vehicle at which a wireless headset is operable; full duplex communication over digitally encrypted DECT protocol links from one the base station; pairing of each particular headset to a particular base station; wireless communications within and exterior to the vehicle; automatic link and channel selection to avoid interference, wherein the selection is transparent to the users; removal of the need to manually select a channel for a wireless headset; and a noise-cancelling microphone with noise threshold, noise attenuation, and line echo cancellation tuned to parameters of the intercom. The improved vehicle crew communications system, including five or less base stations. The improved vehicle crew communications system, including four or less of the wireless headsets. The improved vehicle crew communications system, wherein the microphone is automatically constantly on and the PTT switch provides access to a radio when the PTT switch is activated. The improved vehicle crew communications system, wherein a particular wireless headset of a wireless headset includes: a noise-cancelling microphone; a microphone circuit coupled to the microphone, wherein the microphone circuit employs noise gating tuned to the microphone input of the intercom and further provides balancing of an audio level to allow the user&#39;s voice to break over the noise gate; noise-reduction ear covers; a volume control switch; and a push-to-talk (PTT) switch. The improved vehicle crew communications system, wherein a wireless headset includes a rechargeable headset battery, the system further including a battery charger coupled to the vehicle for charging a rechargeable headset battery. The improved vehicle crew communications system, wherein the base station includes firmware including an adaptive digital signal processing algorithm to reduce side tone from a wireless headset. 
     An improved vehicle crew communications system including: a vehicle capable of carrying a crew, such crew including a plurality of human crew members who are users of the system; a plurality of base stations coupled to the vehicle wherein: each base station of the plurality of base stations provides five channels each having: twelve full-duplex TDMA links; a DECT protocol in the 1920-1930 MHz sub-band; an adaptive DSP algorithm incorporated in firmware for attenuating side tones; and encryption; and the plurality of base stations includes no more than five base stations; an intercom communicatively coupled to: a base station of the plurality of base stations via a microphone input in the intercom, wherein: audio levels from the intercom to the base station are frequency and gain matched to the base station; and audio levels from the base station to the intercom are frequency and gain matched to the intercom; and a radio; four or fewer wireless headsets each wirelessly communicatively coupled via respective TDMA links to particular respective base stations of the plurality of base stations, wherein each the wireless headset includes: a head-engaging web; a noise-cancelling microphone coupled to the web; a microphone circuit coupled to the microphone; a pair of noise-reduction ear covers coupled to the web; a volume control switch coupled to one noise-reduction ear cover of the pair of the noise-reduction ear covers; a push-to-talk (PTT) switch coupled to one noise-reduction ear cover of the pair of the noise-reduction ear covers, wherein the PPT switch is operable to: access the radio; switch the microphone from off to continuously on; or switch the microphone from off to momentarily on; and wherein the improvements comprise: increase in numbers of wireless headsets usable at once with one base station; increase in a distance from the vehicle at which a wireless headset is operable; full duplex communication over digitally encrypted DECT protocol links from each the base station; pairing of each particular headset of a wireless headset to a particular base station; wireless communications within and exterior to the vehicle; automatic link and channel selection to avoid interference, wherein the selection is transparent to the users; removal of the need to manually select a channel for a wireless headset; and a noise-cancelling microphone with noise threshold, noise attenuation, and line echo cancellation tuned to parameters of the intercom. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and 
         FIG. 1  is a diagrammatic view illustrating an exemplary improved vehicle crew communication system, according to an exemplary embodiment of the present invention; 
         FIG. 2  is a diagrammatic view illustrating the exemplary channel and slot configuration of the TDMA embodiment of the present invention; and 
         FIG. 3  is an electrical diagram for an intercom that may be used with the improved vehicle crew communications system, according to an exemplary embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following detailed description of the invention is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding background of the invention or the following detailed description of the drawings. 
     As used and defined herein, “DECT protocol” is interchangeable with “DECT 6.0 protocol” and also refers to compatible follow-on versions of DECT 6.0 protocol. 
       FIG. 1  is a diagrammatic view illustrating an exemplary improved vehicle crew communication system  100 , according to an exemplary embodiment of the present invention. Vehicle  102  is illustrated as a truck, but the invention is not so limited. For example, the vehicle may be, without limitation, a fire engine, an ambulance, or other emergency services vehicle, a crane, a boat, a mining truck, or an aircraft on a taxi-way. Wireless headsets  112 ,  114 ,  116 , and  118  also represent users of such headsets, two of whom ( 112  and  114 ) are in the vehicle  102  and two of whom ( 116  and  118 ) are outside the vehicle  102 . A base station  106  coupled to the vehicle  102  provides full duplex wireless links  120 ,  122 ,  124 , and  126  to headsets  118 ,  116 ,  114 , and  112 , respectively. 
     Headsets  112 ,  114 ,  116 , and  118  have a head-engaging web connecting two noise-reducing ear cups. Headsets  112 ,  114 ,  116 , and  118  have push-to-talk (PTT) capability, provided by a button on an ear cup of each headset  112 ,  114 ,  116 , or  118 , and a microphone with volume control coupled to the head-engaging web. A preferred headset  112 ,  114 ,  116 , or  118  has a constantly open headset microphone and uses the PTT switch to access the radio  130 . A less preferred headset  112 ,  114 ,  116 , or  118  has no radio  130  access and has an open microphone only when the PTT function is activated, preferably by depressing a button on an earpiece of the headset  112 ,  114 ,  116 , or  118 . In another alternate embodiment, for use where background noise is too high, the microphone may be activated by a PTT button. Each headset  112 ,  114 ,  116 , and  118  has a noise cancelling microphone, noise reduction ear covers coupled to the web, and a volume control switch. The noise reduction ear covers include the ear cups, sound-damping foam inside the ear cup, and ear seals around the perimeters of the ear cups. The headset  112 ,  114 ,  116 , or  118  may be designed variously for use under a helmet or hardhat or for use without a helmet. In an alternate embodiment, wireless links  120 ,  122 ,  124 , and  126  may be half-duplex, using an alternate protocol and wireless platform. 
     The number of headsets  112 ,  114 ,  116 , and  118  shown is not intended to limit the invention to four headsets  112 ,  114 ,  116 , and  118 , as will be further discussed below. Headsets  112 ,  114 ,  116 , and  118  incorporate a noise-canceling microphone with a bidirectional (sometimes hyper-cardioid) pattern that cancel the far field sounds and amplify the near field sounds. Noise canceling microphones work better for low frequency noise rather than high frequency noise. In addition, the microphone circuits of headsets  112 ,  114 ,  116 , and  118  employ noise gating. Noise gating means that a threshold is set for the microphone input level, below which everything is treated as noise and therefore is not passed through. Any sound has to be loud enough at near field from the microphone in order to get over the noise gate threshold. To be successful, noise gating requires setting the noise threshold and attenuation level in the headsets  112 ,  114 ,  116 , and  118  to interact correctly with the respective noise gate parameters on the intercom&#39;s  110  microphone input. Another critical feature is the balancing of the audio level for the artificial side tone in order to create the correct psycho-acoustic feedback for the user in order to enable him to break over the noise gate consistently. Unbalanced noise-gating results in clipping off the first syllable(s) of words or having background noise overwhelm the conversation. 
     Inherent in the nature of the DECT 6.0 protocol is a significant delay associated with voice data processing. This delay is approximately 20 ms (10 ms one way) for a signal transmitted from the headset  112 ,  114 ,  116 , or  118  to the base station  106  and into the intercom  110 , looped through the intercom  110  and transmitted back by the base station  106  to the headset  112 ,  114 ,  116 , or  118 . This delay renders the true side tone (the side tone coming back from the intercom  110 ) on the headset  112 ,  114 ,  116 , or  118  extremely echo ridden which causes a significant amount of user dissatisfaction during use. An adaptive DSP algorithm incorporated in the base station firmware called the LEC (Line Echo Canceller), with proper tuning and application-specific parameterization is preferred for reducing line echo. This is a rather sophisticated routine with many parameters that must be tuned just right in order to operate optimally. The function of the LEC is to eliminate (or severely attenuate) a particular wireless headset&#39;s side tone coming back from the intercom while preserving the audio coming from other wireless bases stations  105  and wired headsets  112 ,  114 ,  116 , and  118  connected to other slots on the intercom. This means that the parameters of the LEC as well as the audio levels coming out and going into the base station have to be adjusted just right to match the frequency response and gain (transfer function) of the intercom  110  system in order to achieve a satisfactory echo suppression performance. At the point when the real side tone of the headset (in this case treated as echo by the base station) is eliminated, the artificial side tone on the headset is then enabled. 
     Base station  106  is coupled into intercom  110 , which manages communications switching. Preferably, more than one base station  106  may be coupled to one intercom  110 . For example, up to six base stations may be coupled to a Firecom™ 3020R intercom  110  manufactured by Sonetics Corporation of Portland, Oreg. In the present embodiment, each base station has five channels and up to five headsets may be “paired” to each base station. Preferably, no more than four headsets  112 ,  114 ,  116 , and  118  are in use with one five-channel base station  106  at any given time. Multiple base stations  106  may be used with each intercom  110 , allowing for a large number of headsets  112 ,  114 ,  116 , and  118  per vehicle  102 . 
     Optionally, at least one radio  130 , for long-distance communication outside the vehicle  102 , may be coupled to the intercom  110  to provide all users access to information arriving over the radio. For example, up to two radios  130  may be coupled to a Firecom™ 3020R intercom  110 . Any user of headset  112 ,  114 ,  116 , or  118  may communicate over radio  130  and one user may be assigned a priority radio transmission slot on the intercom  110  allowing priority transmission over the radio  130 . In an alternate embodiment, the preferred slot for radio communication may be switchable. For example, while a fire truck is heading to a fire, the driver may be connected to radio  130 . Once at the fire, the ranking fireman may be switched into the radio  130 . When two radios  130  are coupled to intercom  110 , a faceplate switch enables switching between radios. In an alternate embodiment, the radios  130  may be switched remotely via a switch on a headset  112 ,  114 ,  116 , or  118 . 
     Base station  106  is preferably attached to the vehicle in a high position that avoids proximity to metal in order to minimize interference between metal in the vehicle  102  and the wireless signals going to and from the base station  106 . In a preferred embodiment, the vehicle  102  is designed to accommodate the base station  106  in a position where interference (including antenna pattern skew and RF attenuation) from metal surfaces and objects that are part of the vehicle  102  is minimal. For example, base station may be located high up on a front window of the vehicle  102 . In another preferred embodiment, the base station  106  may be integral to (built into) the vehicle  102  in an advantageous position. In another embodiment, the vehicle  102  body may be made of a material that is at least partially transparent at the operating frequencies of the base station  106  and headsets  112 ,  114 ,  116 , and  118 . As an exemplary embodiment, the vehicle may have a vertical boom extending from a non-metallic vehicle  102  roof, (i.e. fiberglass), to maximize wireless coverage. 
     In a preferred embodiment, the vehicle  102  will have charging stations  136  for the wireless headsets  112 ,  114 ,  116 , and  118 , which is preferably by wires leading from the charger  136  to be plugged in to the headsets  112 ,  114 ,  116 , and  118 . Placement of charger  136  in  FIG. 1  is not intended to be limiting. The headsets  112 ,  114 ,  116 , and  118  preferably operate while charging. In an alternate embodiment, a rechargeable battery station  138  for recharging headset batteries is integral to the vehicle  102 . Placement of battery charger  138  in  FIG. 1  is not intended to be limiting. 
     Depending on the environment in which the vehicle  102  may be used, the vehicle  102  and headsets  112 ,  114 ,  116 , and  118  are preferably made of materials that can withstand environmental influences such as heat, cold, rain, sea water spray, and the like. Further, the headsets  112 ,  114 ,  116 , and  118  preferably comply with occupational safety regulations. 
       FIG. 2  is a diagrammatic view illustrating a snapshot of the exemplary channel  211 - 215  and slot  221 - 232  configuration of an exemplary embodiment of the present invention. The base station  106  preferably provides five channels  211 ,  212 ,  213 ,  214 , and  215  in a DECT 6.0 protocol Unlicensed Personal Communications Services (UPCS) at 1920-1930 MHz sub-band. Each channel preferably provides twelve TDMA slots  221 ,  222 ,  223 ,  224 ,  225 ,  226 ,  227 ,  228 ,  229 ,  230 ,  231 , and  232 . This theoretically allows up to sixty headsets per base station  106 , although sixty headsets is usually not operationally preferred. Each headset  112 ,  114 ,  116 ,  118 , are paired to a particular base station  106  and cannot be used with other base stations  106  without reprogramming. Base station  106  is preferably coupled to intercom  110  through a connector  204 , such as an RJ-12 connector  204 . Intercom  110  may have multiple ports  202  (one labeled, five shown) for coupling in additional base stations  106  with additional headsets. Intercom  110  may also have a speaker with volume control (not shown). 
     Voice communications over wireless links  120 ,  122 ,  124 , and  126  are digital and are encrypted to reduce the risk of interception and spoofing. The DECT 6.0 protocol detects which slot  221 - 232  in channels  211 - 215  has the lowest level of interference based on a preset Radio Signal Strength Indication (RSSI) and automatically switches to that particular slot in that particular channel  211 - 215 . Keeping the number of headsets in use below sixty supports this capability: if every channel  211 - 215  is saturated, there are no available slots to switch to when interference is to be avoided. The switching between slots  221 - 232  and channels  211 - 215  during a given conversation is automatic and transparent to the user. 
     In other frequency bands, more than five channels may be available and a larger number of headsets may be supported by appropriately designed base stations  106 . 
       FIG. 3  is an electrical diagram for an intercom  110  that may be used with the improved vehicle crew communications system  100 , according to an exemplary embodiment of the present invention. Headset  118  is wirelessly linked to multiple headset base station  106  which feeds the microphone audio through preamp  333  and then into summing amplifier  302 . The output of summing amplifier  302  goes to audio amplifiers  318 ,  319 , and  320 . The output of audio amplifier  320  is coupled to multiple-headset base station  106  and transmitted wirelessly to headset  118  and also to single-headset base station  310  and transmitted wirelessly to headset  308 . Audio amplifier  319  exemplifies an audio amplifier that supplies other audio loads (not shown) having impedance different from the base stations  310  and  106 . Audio amplifier  318  supplies audio signals to wired headsets  304  and  306 . Preamp  330  amplifies the microphone audio from wired headset  304  and feeds the amplified audio to summing amplifier  302 . Preamp  331  amplifies the microphone audio from wired headset  306  and feeds the amplified audio to summing amplifier  302 . Preamp  332  amplifies the microphone audio from single-headset base station  310  which received the microphone audio from headset  308  and feeds the amplified audio to summing amplifier  302 . A plurality of multiple-headset base stations  106  may be connected with the addition of more audio amplifiers and preamps. 
     The improvements represented in the present invention include an increase in the number of headsets  112 ,  114 ,  116 , and  118 , an increase in range for the headsets  112 ,  114 ,  116 , and  118 , full duplex communication over digitally encrypted DECT 6.0 protocol links from one base station  106  to a plurality of headsets  112 ,  114 ,  116 , and  118 , pairing of headsets  112 ,  114 ,  116 , and  118  with particular base stations  106 , the use of only wireless technology for communications inside and within range of the vehicle, automatic channel selection to minimally-interfered-with channels, and removal of the need for manual channel selection in a wireless headset. Also, the combination of the noise-cancelling microphone with noise threshold, noise attenuation, and line echo cancellation tuned to intercom  110  parameters is regarded as novel. 
     Although applicant has described applicant&#39;s preferred embodiments of this invention, it will be understood that the broadest scope of this invention includes alternate embodiments such as those using diverse types of materials, circuits, and appliances that accomplish the same purpose in the same way. Such scope is limited only by the below claims as read in connection with the above specification. Further, many other advantages of applicant&#39;s invention will be apparent to those skilled in the art who are enlightened by the above descriptions and the below claims.