CA2675938A1

CA2675938A1 - Communications system and protocol for medical environment

Info

Publication number: CA2675938A1
Application number: CA002675938A
Authority: CA
Inventors: Michael C. Perkins; Reuben P. Garcia; Lawrence W. Gallagher; David C. Parrish
Original assignee: Individual
Current assignee: Rauland Borg Corp
Priority date: 2007-02-22
Filing date: 2007-02-22
Publication date: 2008-08-28
Anticipated expiration: 2027-02-22
Also published as: WO2008103177A1; CA2675938C

Abstract

A communications system and protocol are described for wirelessly interconnecting a pair of bed and wall units that communicate the patient information, including bed exit alerts, from the patient supporting equipment to the hospital nurse call system. A linking procedure is provided for establishing a communications link to interconnect the pair of units, wherein the communications link fails upon detection of a third communications device simultaneously undergoing the link attempt mode. In one embodiment, the system provides for advanced collision detection by monitoring corruption of the end-of-packet byte within the periodic check- in message sequences between the linked units to prevent data corruption and future collisions. To ensure prompt interconnection of units, embodiments of the invention provide for a link reminder to alert the health care provider to initiate the steps for linking the bed and wall units whenever two or more unlinked units are in proximity.

Description

COMMUhTICATIONS SYSTEM AND PROTOCOL FOR MEDICAL ENVIRONMENT
FIELD OF THE INVENTION

[0001] This invention relates generally to the field of communications and more specifically to the field of medical connnunications devices.

BACKGROUND OF THE INVENTION

[0002] Modern health care environinents place heavy burdens on medical personnel responsible for a continuously growing number of patients. Nursing shortages and heavy workloads continue to be the norm in most modeni hospitals. Nursing and other front line medical caregivers are typically responsible for monitoring and reporting patient conditions. A

patient's post-operative recovery, for example, often requires monitoring and restricting patient movement. This task is frequently complicated wlien dealing with patients who are confused or unable to understand the caregiver's instructions and are at risk of injury due to their propensity for excessive movement.

[0003] Patient movement and bed position detection systems provide monitoring and alerting capabilities by conveying to care givuzg persoimel a patient's movement and/or position on the bed. These systems provide for remote monitoring and alerting by employing sensors incorporated into hospital beds or other patient supporting equipment that interface with a nurse call system to relay the sensor data to a nursing station or a telemetry unit.
Wlien the system detects that a patient has left the bed, changed positions and/or moved the bed controls in a way that does not colnply with an allowed range of motion, nursing personnel are alerted to take appropriate action. Typically, patient movement and position sensors mounted 'ul the bed interface with a control unit located on the bed. The control unit transinits the patient data to the nursing station via a cable that connects the control unit and a nurse call system interface located in the patient's room.

[0004] Patient beds and other patient equipment are often moved about a hospital. Upon moving the bed to another location, the cable connecting the bed to the nurse call system is disconnected for transport of the bed and then reconnected when the bed is prepared at its new location. Because the cable is a physical tether, it is easy for hospital personnel to forget to disconnect the cable before moving the bed or any other equipment cabled to the wall, causing dainage to the cables and to the com-lectors on the bed and the wall Additionally, when the bed is being prepared at a new location, hospital personnel do not have the physical reminder to coiu7ect the cable.

BRIEF SUMMARY OF THE INVENTION

[0005] A wireless communications link and associated protocol interconnect a pair of bed and wall units that coiinnunicate patient information, including bed exit alerts, from a patient supporting equipment to a hospital nurse call system. In one einbodiment, the bed/wall uiiit pair operates within unlicensed spectrum and, tlierefore, takes into account possibility of congestion and interference in order to provide safe and reliable connection to the nurse call system.
Specifically, a linldng procedure aids the establislunent of a coininunications link between the bed and wall units and prevents unintended cross luiking of the paired units to other nearby bed and wall units. During the linking procedure, the establishment of the cormnunications link fails upon detection of a third coininunications device such as a bed or wall unit attempting to participate in the linking process.

[0006] Once established, the communications link is maintained by periodically exchanging link status or check-in message sequences between the linlced bed/wall pair.
The processing of the messages includes detecting collisions with link status messages generated by other linked bed/wall pairs. Early detection of collisions or interference among linlcs is achieved by monitoring corruption of an end-of-packet or tail-feather byte within the periodic messages. As link status messages from different links slowly drift toward one anotlier, the end-of-packet byte in one of the two messages will coiTupt first. By responding to corruption of the end-of-packet byte, the data in the packet is saved so that the integrity of the link status message remains intact.
Early detection of the collision enables the message to be adjusted either in time or frequency to avoid corruption of the links' integrity.

[0007] In one embodiment, the periodic linlc messages are time shifted upon detection of a collision of linlc status messages, which moves the messages away from the colliding messages that are also periodic. Although the interfering messages may share the saine or a similar repetition period, by shiftuig the timing of one of the messages, the messages of one link no longer overlap messages of the other link detected by the collision. Other features include monitoring for combinations of first-try checlc-in message failure and first-resend success, as strong indications of colliding units, and adjusting the nominal time slot of periodic checlc-in messages. Altei7iatively, the linked bed/wall unit pair shifts to another operating chaiulel upon detection of link status message collisions. To prevent interference from other devices sharing the same specti-u.m, the system also provides for monitoring channel noise and moving to a different operating channel to evade other interfering devices.

[0008] Preferably, the bed unit includes a local power source such as a battery. To ensure long lasting operation, the bed unit enters an idle sleep mode by temporarily powering down its transceiver circuitry.

[0009] To ensure proinpt interconnection of units, embodiinents of the invention provide for a linlc reminder to alert the health care provider to initiate the steps for linking the bed and wall units whenever two or more uiilinked uiiits are in proxiinity. The system broadcasts lii-ilc reminder messages to elicit reply messages from one or more nearby unlinlced units and activates a link reminder alert upon receipt of multiple replies fioxn the same ui-ilinked unit. When the system operates on inultiple frequencies, w-ilinked units transmit link reminder messages on each of the system channels.

BRIEF DESCRIPTION OF TFIE SEVERAL VIEWS OF 'I']HE DRAWING(S) [0010] While the appended claims set forth the features of the preserit invention with particularity, the invention and its advantages are best understood from the following detailed description taken in conjunction witlz the accolnpanying drawings, of which:

[0011] FIGURE 1 is a schematic diagram illustrating a llospital facility enviromnent having inultiple liospital beds each wirelessly connected to a hospital monitoring and alerting system via a pairs of bed and wall units;

[0012] FIGS. 2 and 3 are front and side views of the bed unit of FIG. 1;

[0013] FIGS. 4 and 5 are front and side views of the wall unit of FIG. 1;

[0014] FIG. 6 is a scllematic diagrain of the RF and controller circuitry in the bed unit of FIGS. 1-3;

[0015] FIG. 7 is a scliematic diagrain of the RF and controller circuitry in the wall unit of FIGS. 1, 4 and 5;

[0016] FIG. 8 illustrates the format of a communications fiame in accordance with the communications protocol of the invention;

[0017] FIG. 9 is a timing diagrain illustrating the successful completion of the linking process to establish a coininunications link between a bed/wall unit pair of FIG. 1;

[0018] FIGS. 10 and 11 are timing diagrams illustrating different scenarios leading to failure of the linking process of FIG. 9;

[0019] FIG. 12 is a tiining diagram illustrating the adjustment of a time window in which a bed unit of FIGS. 1-3 periodically communicates with its mated wall unit to maintain the coininunications link, where the time window is adjusted pursuant to advanced detection of collisions of check-in message sequences associated with a bed/wall unit pair of FIG. 1;

[0020] FIG. 13 is a tiining diagram illustrating the operation of the linlc reminder to alert the health care provider to initiate the linking process of FIG. 9;

[0021] FIG. 14 is a state diagrain sliowing the relationship ainong various operating states of the bed and wall units, including Linking Process, L'uiked Idle, Check-in Message, Call Message and Unlinked Idle states;

[0022] FIG. 15 is a flowchart illustrating the detailed operation of the Linking Process State of Fig. 14;

[0023] FIG. 16 is a flowchart illustrating the detailed operation of the Linked Idle State of Fig. 14;

[0024] FIG. 17 is a flowchart illustrating the detailed operation of the Check-in Message State of Fig. 14;

[0025] FIG. 18 is a flowchart illustrating the detailed operation of the Call Message State of Fig. 14; and [0026] FIG. 19 is a flowchart illustrating the detailed operation of the Unlinked Idle State of Fig. 14.

DETAILED DESCRIPTION OF THE INVENTION

[0027] Turning to the drawings and referring first to Figure 1, a typical hospital facility enviromnent has multiple hospital beds connected to a hospital monitoring and alerting system.
In Figure 1, only two hospital rooms l0a and l Ob are illustrated. Each of the rooms l0a and l Ob are identically equipped.

[0028] For ease of explanation, whenever detailed reference is made hereinafter to the equipinent in one of the rooms l0a and 10b, the description applies equally well to the other room in Figure 1, unless indicated otherwise. Moreover, Figure 1 is representative of a larger enviromnent such as a hospital that may include many more rooms such as the two illustrated in Figure 1 that are also equipped in the saine or similar mamler. All of the rooms may be connected to a common nurse call system as suggested by Figure 1 or there may be several nurse call systems with each of them comiecting a group of rooms. All such networking arcliitectures and others are conteinplated by the detailed description set forth herein.

[0029] To communicate patient infonnation from the hospital room l0a to a monitor 12 at a remote nursing station, a bed and wall unit pair 14 and 16, respectively, is associated with a mobile hospital bed 26 through a wireless cominunications link. 22.
Preferably, the coininunications lin.k 22 operates within an ui-dicensed frequency band, such as Industrial, Scientific, and Medical (ISM) frequencies allocated by the United States Federal Communications Coinmission (FCC) to be einployed for low-power/short-range wireless coininunications. To reduce the chance of interference from other devices sharing the ISM
frequencies, the communications linlc 22 preferably operates within the 902 -928 MHz ISM
frequency band and complies with the correspond'uig maximum transinit power limitations designated by the FCC for devices operating within this frequency range. Other conteinplated frequency bands include other available ISM frequency bands, such as 2.4 GHz and 5.8 GHz bands. In the illustrated embodiment, the bed unit 14 is attached to the mobile liospital bed 26 for collecting the patient information, which includes patient occupancy, nurse call, call assurance, and system status signaling.

[0030] To convey the nurse call and call assurance sigiialing, the bed unit 14 interfaces with the patient comi.nunications module 46, which is located within the siderail 50. To coininunicate with the health care provider 54, a patient initiates a nurse call via the coininunications module 46. Once the patient places a nurse call, the communications module 46 generates a call assurance signal by activating a visual indicator (not shown), such as a status LED, to indicate that a nurse call has been placed. Similarly, when the maintenance of the conu.nunications link.
22 is in jeopardy due to low battery power at the bed unit 14, or wlien the coinmunications link 22 is lost, such as due to poor signal conditions or movement of the bed 26, the bed utut 14 or the wall unit 16 generates a "bed out" signal reflecting the system status.

[0031] Furthermore, to collect the patient occupancy information, a bed sensor 30 measures the interaction of the patient's body with the bed fraine 34 and conveys the collected information to the bed unit 14 via a cable 42. Alternatively, there may be a wireless connection between the bed unit 14 and the bed sensor 30. An exainple of a bed sensor equipped hospital bed is a Chaperone center of gravity bed exit system manufactured by Stryker Corporation located at 2825 Airview Boulevard, Kalainazoo, Miclzigan 49002. A typical bed exit system includes one or more occupancy sensors 30 distributed along a bed fraine 34 to collect and analyze the weight information and determine the patient's occupancy status, such as wlzether the patient has left the bed 26 and/or the patient's position on the bed 26. In the illustrated einbodiunent, the bed sensor 30 is a pad type sensor placed on top of the mattress 38, while other embodiments include load cell sensors incorporated into the bed fiame 34. The patient occupancy information generated by the bed exit system also uicludes a bed exit alann signal generated by the occupancy sensor 30 wli.en the patient moves off the bed fraine 34. The patient occupancy iiifonnation fiurtller includes patient weight, bedrail height, bed height, bralce status, and bed support elevation angle.

[0032] Upon collecting the patient u.ifoimation, the bed unit 14 cornmunicates witli the wall unit 16 via the colnrnunications link 22. While the bed unit 14 is capable of mobility due to its attachinent to the mobile hospital bed 26, each wall unit 16 remains stationary in its associated hospital room 10a. Therefore, the wall unit 16 is able to communicate with the bed unit 14 when the bed unit 14 moves in its proximity. The wall unit 16, in turn, conveys the collected infonnation to the health care provider 54 via the nurse call system 56. The nurse call system 56 connects a plurality of rooms 10a, 10b, each having a bed 26, 28 and a correspond'u-ig bed/wall unit pairs 14/16,and 18/20 to one or more nursing station monitors 12 for allowing the healtlz care provider 54 to monitor the patient inforrnation. Exeinplary nurse call systems include any one of a line of Responder integrated health care coininunications systems manufactured by the Rauland Borg Corporation located at 3450 West Oakton Street, Skokie, Illinois 60076. In one embodiment, the nurse call system 56 integrates with an IP-based local area network to accumulate the patient infoimation fioin a plurality of mobile hospital beds 26, 28 via coiulections 58, 60. To provide a local indication of on-going bed exit and nurse call events to the health care provider 54, the wall unit 16 additionally connects to an external room transducer 15, which is mounted to one of the internal or external walls of each room 10a and l Ob. The room transducer 15 provides an audio alert, such as a speaker or a buzzer tone, for the health care provider 54 to check on the patient within the room. Alternatively, the transducer 15 provides a visual alert, such as a flashing light, or a combination of audio and visual alerts.

[0033] To establish the cormnunications link 22, the health care provider interacts witli user interfaces at each of the bed and wall units, such as by pressing a button on each of the units. As illustrated in Figures 2 and 3, to link the bed unit 14 witll the wall unit 16, the health care provider presses a liiik button on one or both of the user interfaces 64 and 78 of the bed and wall units 14 and 16, respectively. Preferably, it does not matter whetlier the health care provider first presses the link button 62 or the link button 76 to initiate the linking process. Pressuig a link button on either the bed unit 14 or the wall unit 16 initiates a timer duruig whicli the health care provider is required to press the corresponding link button on the other unit of the pair to be linked. In one einbod'unent, the lii-Acing process timer is set to five (5) seconds fi-om the time the health care provider activates the link button 62 or the link button 76. Each unit's link indicator 66, 80 flashes during the linking process. Once the liiilcing process is complete and the communications liiilc 22 between the linked bed/wall unit pair is established, the wall unit's link indicator 801ights up continuously. Since the bed unit is preferably battery operated, while the wall unit is powered through its connection to the nurse call system, the bed uliit's link indicator 66 tiu=iis off to save battery power after the coinmunications linlc 22 is establislled.

[0034] If the linlc attempt is unsuccessful, one or both of the bed unit 14 and the wall unit 16 sounds a continuous tone for a predetermined duration. In the illustrated embodiment, the unit that initiates the link attempt signals a failure since the other unit may not be aware of the atteinpt.

[0035] To immediately silence the link failure tone, the health care provider presses the bed unit's unliiilc button 68 and the wall unit's cancel button 82. Similarly, when the bed 26 is moved to another hospital room, the health care provider manually unlinlcs a linked bed/wall unit pair by pressing the unlink button 68 on the bed transceiver unit 14.
Ufflinking the units also generates a "bed out" signal, which the wall unit 16 relays to the nursulg station moliitor 12 to alert the caregiver personnel that the commutiications link 22 between the two units is lost. The bed unit also generates a "bed out" signal and activates the low battery indicator 70 when its battery level drops below a predeterinined threshold. When the bed unit 14 is linked to the wall unit 16, the wall unit 16 siznilarly activates its low battery indicator 84 upon relaying the "bed out" signal and the associated low battery warning to the nursing station. The low battery threshold is preferably set so as to allow continued operation of the bed unit 14 for a number of days or weeks after the activation of the low batteiy indicators in order to provide the caregiver with sufficient tiune to cliange the batteries.

[0036] Preferably, the bed and wall units include a linlc reminder feature that alerts the health care personnel to initiate the linking process whenever an urilii-Aced bed unit 14 moves in proximity of the in-Ainlced wall unit 16. The bed unit 14 emits an audio reminder, such as a short chiip, to proinpt the health care persoimel to initiate the linking process and press the link button 62 or the liillc button 76. Altenlatively, the wall unit 16 can provide the reminder or even both units 14 and 16 can provide reininders, including a visual reminder, such as flashing the link status LEDs 66, 80 at one or both units, instead of or in addition to the audio reminder.

[0037] If the caregiver decides that the cominunications liiilc 22 should not be established between the two units, he or she presses the unlinlc button 68 on the bed unit 14 in order to silence the link reminder alann. Preferably, the link reminder returns after a predetermined time, such as one hour, if the two ui-Ainked units still remain unlinked and in proxiinity. However, to provide a link reminder witli respect to a new pair of unlinked units, such as when a previously silenced unlinked bed unit is moved in proxiinity of a different unlinked wall unit, the link reminder returns before the one hour period. Additional aspects of operation of the link reminder feature are discussed in more detail below in connection with the state diagrams and flowcharts of Figures 13 and 19.

[0038] As illustrated in Figure 4, to convey the patient inforination from the mobile liospital bed 26 to a nearby wall unit 16, the bed unit 14 attaches to the bed frame 34 via fasteners 72, 74 and interfaces with the bed sensor 30 and the cominiulications module 46 via a connector 96.
Specifically, the bed uiiit con.nector 96 mates with a bed interface comiector 97 for routing the patient occupancy infonnation (e.g., bed exit alarms), as well as nurse call and call assurance signaling, to the bed unit 14 via cables 42 and 95 respectively. The connector pair 96 and 97 uses a DB37 pin type comlection. Similarly, as shown in Figure 5, the wall unit 16 interfaces with the nurse call system 56 and room transducer 15 via a connector pair 93 and 94, whicli also einploys a DB37 pin type colulection. Preferably, the wall unit 16 is powered through the connector 94 via a coiTesponding pin connection to the nurse call system 56.
To provide an alternative power source, which can be used during the maintenance of the nurse call system 56, for exainple, the wall unit 16 includes an external power port 86. Wall fasteners 88, 90 ensure that the comiector 94 does not come loose from its wall receptacle, while the chain pin 92 provides an attaclunent point for a small wall chain to ensure that the wall uliit 16 is not inisplaced when it is disconnected from the wall receptacle, such as during the system maintenance.

[0039] Circuitry comprising each of the bed unit 14 and wall unit 16 includes radio frequency (RF) and controller components to manage the establislunent and maintenaiice of the coinmunications link 22. The RF component is a transceiver for supporting the wireless coinlnunications link 22. The controller component cooperates with the transceiver to support the processes described herein.

[0040] RefeiTing to Figures 6 and 7, the bed interface circuitry 98 of the bed unit 14 collects the patient inforination from the bed sensor 30, as well as the commuiiications module 46 (Fig.
1), and provides it to the controller 100 for processing. In turn, the bed unit controller 100, as well as the wall unit controller 114, manage the establishinent, operation, aiid status reporting of the communications link 22, 24, via their respective RF circuitiy components, namely the transceivers 102, 112, in order to relay the collected patient infonnation between the units and to the nurse call system 56 and/or the room transducer 15. An exemplary embodiinent of the controllers 100, 114 is a model CY8C27443 manufactured by Cypress Semiconductor Coiporation located at 198 Champion Ct., San Jose, California 95134. An exemplary einbodiment of the transceiver circuitry 102, 112 is a model XE1203F
transceiver module manufactured by Semtech Corporation, located at 200 F1ynn Road, Camarillo, California 93012.
Preferably, each of the bed and wall units 14 and 16 includes an internal anteima 104, 116, respectively, coupled to the transceiver circuitry 102, 112 for transmitting the patient information between the units.

[0041] When the bed unit 14 is in its unlinked state and its controller 100 detects a nearby unlinked wall unit 16, the controller drives the link reminder signal generator 106 by outputting an activation signal to the linlc reminder signal generator, which responds by generating a link reminder alaim that can be a sound generated by a transducer 108 and/or a visual proinpt at the user interface 64. Altliough in the illustrated embodiinent the linlc reininder signal generator 106 is external to the controller 100, the generator and the controller may be a single component. In the illustrated einbodiment, the transducer 108 provides an audio alert and may be a piezoelectric buzzer that emits short chirping sounds, while other embodiments include visual link reminders at the interface 64, such as flashing LEDs, as well as coinbinations of audio, visual, and other types of alert indicators. In yet another embodiment, the wall unit 16 also includes the link reminder signal generator and trailsducer circuitry for alerting the health care personnel of its unlinlced status.

[0042] In order for the cormnunications linlc 22 to be a completely wireless connection, the bed unit 14 includes a local power source such as one or more batteries 110.
Battery operation enables the unlinked bed unit 14 to operate continuously and witliout relying on hospital personnel to attach a power source. However, external power sources can also provide power to the bed unit 14. For exainple, power can be derived from a power source primarily intended for the bed 26. If total power consumption is very low, the bed unit 14 may even be powered by an electromagnetic source remote from the unit and the bed in a manner similar to passive transponders. When powered by batteries 110, power consuinption is minimized by includ'u1g a sleep mode for the electronics wherein the controller 100 periodically directs the bed unit 14 to enter a partially powered down state. Unlike the bed unit 14, however, the wall unit 16 is usually fixed in the hospital room and, therefore, has access to the hospital's primary power resources.
Thus, the wall unit need not require power conservation tecluiiques although it still may incorporate them if desired. As illustrated in Figure 7, the wall unit 16 draws power from the nurse call system power source 55 via a pin connection at its comiector interface 94 (Figure 5).

[0043] To provide for message transmission between the bed and wall units, the message format employed by the communications link 22 includes a plurality of message fields corresponding to message routing, data payload, and error detection signaling.
In Figure 8, a message paclcet for transmission by the cormnunications link 22 is a message fraine 118 coinprising a 22 byte sequence preceded by a preamble 120 to allow the transceiver 102, 112 in each of the bed and wall units 14 and 16 to lock onto the incoming message data stream in a conventional manner. The preamble 120 is a known or expected bit sequence that the receiving bed or wall unit 14, 16 discards after loclcing onto the message streain.
Thus, the receiving bed or wall unit 14, 16 does not include the preainble 120 in the message decodiizg, cyclic redundancy code (CRC), and message byte count calculations.

[0044] Proceeding down the message byte sequence, message bytes 1- 4 include a fixed pattern block 122, which comprises the same four hexadecimal bytes within each message fraine 118. During system testing and maintenance, the fixed pattern block 122 enables a test receiver to log all message traffic on a given channel witliout concern for the source address 126 in the transmission packet, which is exchanged by the bed and wall units during the establislunent of the communications linlc 22. When a health care provider initiates the linking process by pressing the linlc button 68, 76 at either the bed or the wall unit 14, 16, the bed unit transmits a message packet witli a Liiik Request Broadcast Code (LRBC) within the field 124 corresponding to bytes 5 througli 8 of the message frame 118. Alternatively, when the bed and wall units 14, 16 are linked, the message field 124 includes a destination address of the bed or wall unit, depending on the originating unit, that is the address of the intended recipient of the message frame 118. Duruzg the setup of the communications link 22, the bed and wall units exchange their unique addresses, which correspond to device serial nuinbers. Similarly, the message field 126 (bytes 9-12) contains the source address, or serial nuinber, of the transmitting device. Other einbodiments include exchanging Media Access Control (MAC) addresses between the units to designate destination and source addresses among the devices.

[0045] To keep track of the message exchange and to identify the conununicating devices, the message frame 118 includes a message sequence nuinber counter 128 and a device type field 130 (bytes 13, 14). The message sequence number counter 128 keeps track of the message session nuinber for the corresponding device within the communications link 22. When the cominunications liiik 22 is established between a bed/wall unit pair, the device type field 130 identifies each communicating device as a bed or wall unit, respectively. The device type field 130 also identifies additional device types wlien the communications link 22 includes other devices, such as a wall-inounted emergency push button station and/or a pull cord station for generating a nurse call signal.

[0046] The status bytes field 132 (bytes 15-17) relays additional message data and patient infonnation, such as a nurse call signal uidicator, a bed exit alailn indicator, a bed out alarm indicator, linlc reminder signaling, and various link status indicators, including periodic liilk status request or "clleclc-in" signaling between the linked units. The message type field 134 (byte 18), in turn, includes "Ack" indicators sent in response to a successful receipt of certain messages, as well as "Nak" indicators sent u1 response to messages having CRC
errors identified by comparing the received message CRC to the transinitted CRC bytes 136 (bytes 19-2 1).
Message type field 134 also relays link connection cormnands between the bed and wall units.
As discussed in more detail in connection with Figure 12 below, the transmission protocol also provides advanced collision detection by monitoring for corruption of the last byte (byte 22), called the end-of-packet (EOP) or "tail feather" byte 138, in transinission of Ack messages sent in response to periodic check-in messages. The tail feather byte 138 is not used to calculate the CRC value. Tlierefore, Ack messages having good CRC values aizd uncorrupted data payloads, but having a coiTupted tail feather byte 138, provide an early indication of collisions of periodic check-in message sequences between multiple bed/wall unit pairs. Upon detection of colTuption of the tail feather byte 138, the transmission protocol includes time or frequency shifting the next periodic transmission of check-in or link status messages by a random delay in order to prevent data corruption.

[0047] To reduce the overall number of messages exchanged between the linked bed/wall unit pairs and, consequently, extend each bed unit's battery life, the message protocol furtlier provides for transmission of full fraines at all times between both units within the pair, including when the message type byte 134 contains an Ack or a Nak indicator. This allows inclusion of additional data within the message fraines containing the Ack or Nak signaluig, thereby reducing the need for separate data traiisinissions.

[0048] The tiining diagrams of Figures 9-11 are exeinplary scenarios related to establisliing the cominunications link 22. Figure 9, for exainple, depicts a transmission protocol that results in successfully establishing the coinmunications link 22, where the health care provider initiates the linlcing process by pressing each of the link buttons 62, 76 on the bed/wall unit pair 14/16 within a predetennined amount of time 140. The timer 140 is set to allow the health care provider sufficient tiine, such as five (5) seconds, to press the linlc button on the second unit after pressing the linlc button on the first unit. During this tune period, the bed unit 14 transmits a liiilc request broadcast code (LRBC) 142, labeled "Link Request BUl" to indicate a linlc request from a first bed unit, and waits to receive an aclcnowledgment 144, labeled "Ack WUl" to indicate an aclcnowledgement from a first wall unit, from a nearby wall unit 16.

[0049] Since the bed and wall units 14, 16 exchange their unique addresses to establish the coininunications linlc 22, the bed unit is initially unaware of which wall unit will reply to its linlc request. Therefore, when the coinmunications link 22 is between oidy one wall unit and one bed unit, it is desirable to prevent the occuiTence of inadvertently cross liiAcing the pairs of units in two different rooms l0a and l Ob (Figure 1). For example, if the two bed units 14, 18 in the adjacent hospital rooms 10a, 10b initiate the linlcing process at about the saine time, there is an opportunity for each of the units to linlc to the wall unit in the otller room. Therefore, after exchanging their unique addresses included in the initial linlc request broadcast code and aclaiowledgement messages 142, 144, the bed and wall uiiits 14, 16 wait for another predetermined duration 146 in Figure 9 to receive linlcrequests or acknowledgements from other nearby units, such as the units 18 and/or 20 iui the other room in Figure 1, in order to ensure that cross linking of two pairs of units has not occurred.

[0050] In one elnbodiment, the timer 146 is also set to five (5) seconds. If the timer 146 expires without detection of a linlc request or an aclcnowledgement having an address different from either of the original addresses within the pair 14, 16, the communications linlc is established after the bed u.n.it 14 transinits a link confinnation message 148 and receives an acknowledgement 150 from its corresponding wall unit 16. Otherwise, the link fails when, prior to the expiration of the linlcing timer 146, the wall unit 16 receives a link request 152 having a bed unit address different from that in the original link request 142 (Figure 10), or when the bed unit 14 receives an acknowledgement 154 having a wall unit address different from that in the original aclcnowledginent 144 (Figure 11).

[0051] Instead of establishing one-to-one communication links 22 between bed and wall units, the communications link can also be one-to-many in that one of the wall units 16 can support cominunications liiiks 22 to several bed units 14. In this case, when the healtlz care provider presses the wall unit's 161ink button, the wall unit sends out a periodic linking beacon message and listens for reply messages from one or more nearby bed units 14 once the liealth care provider presses their corresponding linlc buttons. In this scenario, the wall unit 16 remains in the linking mode for a predetennined duration, such as 5 seconds, during which it listens for bed unit replies. Upon receipt of one or more bed unit reply messages, the wall unit 16 sends out linlc confinnation messages addressed specifically to each of the bed units 14 that replied, thereby forming inultiple bed/wall unit pairs 14, 16, where all of the coimnunications linlcs 22 have a coinmon wall unit and a utiique bed unit. In this embodiment, to prevent cross linking the bed units 14 with more than one wall unit, such as when multiple wall units 16 are located in adjacent hospital rooms, each of the bed units 14 fails the linking process if it receives linking beacon messages from more than one wall unit 16.

[0052] Once the bed and wall units 14, 16 are linlced, the units periodically exchange check-in message sequences in order to check the integrity of the communications linlc 22 between the units. When multiple linked pairs of units are in proxiinity, such as when a bed/wall unit pair 14, 16 in hospital room l0a is adjacent to another linked bed/wall unit pair in room 10b, each pair of units undergoes its own periodic exchange of check-in message sequences, as illustrated in Figure 12.

[0053] Either the bed unit 14 or the wall unit 16 may originate the periodic check-in message transmissions, though it is preferable in this einbodiment for the bed unit to initiate all colnlnunications. Since the bed unit 14 is preferably battery operated, its transceiver circuitry 102 is teinporarily powered down to save battery power after its coininunications link 22 is established. In the absence of otlzer transmissions, such as bed exit a.nd/or bed out alarms, the controller 100 of each bed unit 14 periodically wakes up the transceiver circuitry 102 to ensure the coininunications link 22 is alive at the other unit by sending a checlc-in message 156, 158 (Figure 12) to its coiTesponding wall unit 16 and waituig for the subsequent acknowledgement (Ack) message 160, 162 from its wall unit 16.

[0054] There is a tendency for the endpoints of the periodic check-in and Ack message transmissions in one liiilc 22 to gradually drift in time with respect to the same signals ui another link due to iidzerent differences in each unit's timing circuitry. This gradual drift 164 ui the clieck-in message transmissions, for exainple, in a commluzications link 22 may result in a message collision 166 due to a teinporal overlap between the end of one of the periodic checlc-in transinission sequences 168, 170 for one pair and the beguuiing of a corresponding check-in transmission sequence 172, 174 for another co-chaiulel pair. Therefore, the message protocol provides advanced collision detection by monitoring for corruption of the end-of-packet (EOP) or "tail feather" byte 138 (Figure 8), in transmission of messages from the wall unit 16.

[0055] Specifically, when the bed unit 14 receives an Ack message 170 from the mated wall unit 16 with good CRC but with a coiTupted EOP byte 138, the message protocol assumes the leading edge 176 of another checlc-in inessage 172, belonging to a different coinmunications lilik 22, is begiiuiing to overlap the trailing edge 178 of the Ack message 170.
Since all linked bed units 14 normally transmit the initial check-in messages at a fixed period 180 in Figure 12, there is a high probability that the collision will reoccur during the next periodic transmission of the clleck-in message sequences in each of the links 22. To prevent reoccurrence of collisions, the bed unit 14 that detected the corrupted EOP byte 138 adds a one-time random delay interval 182 to its next check-in period 180, tliereby permanently sliifting the nominal time slot of its periodic check-in message sequences with respect to another bed/wall unit pair. After the random delay 182, transmissions of check-in message sequences 184, 186 and 188, 190 continue according to the original check-in period 180. While the illustrated einbodiment allocates a single byte 138 for the EOP marker, other embodiments include allocating a plurality of EOP
bytes at the tail end of the message fraine 118 (Figure 8) in order to enhance tlie ability to detect another iinpending collision before the data payload is affected.

[0056] In the scenario illustrated in Figure 12, the collision 166 corrupted the data payload within the leading edge of the check-in message 176, thereby resulting in a CRC eiTor at the corresponding wall unit. To indicate a CRC error, the wall unit 16 receiving the corrupted checlc-in message 176 transmits a Nalc message 174. Upon receipt of the Nalc message 174, the bed unit 14 witliin this pair initiates a retry transmission of the check-in message 192 after a random delay 194. In this case, the bed unit receives an Ack message 196, indicating a successful receipt of the check-in message 192 by its corresponding wall unit 16. In this illustrated einbodiment, unlike the situation in which a message is received having good CRC
but corrupted EOP or tail featlier byte 138, which provide an early indication of a collision prior to data corruption, when the bed unit 14 receives a transmission having bad CRC or including a Nak message, it resends the check-in message after a random delay 194. In this case, however, the bed unit 14 does not add the random delay 194 to the next check-in message period 180. Iri other words, the bed unit 14 still transmits the next check-in message 198 after a check-in period 180 referenced from the corrupted check-in message 172. In tliis case, the bed unit does not change its nominal time slot for subsequent check-in message tra.iismissions because the CRC
eiTor also could have been caused by reasons other than a collision with another bed/wall unit pair's periodic checlc-in message sequence, such as due to a signal fade.

[0057] In addition to detecting gradual collisions by monitoring corruption of the end-of-paclcet byte, the communications link 22 is also managed so that the bed unit's nominal time slot for transmission of periodic check-in messages is monitored for sudden collisions. The monitoring detects successive occurrences of checlc-in message retries followed by successful receipt of Ack messages. This method of check-in message time slot management detects a sudden and recun-ing collision of check-in message sequences that occur after one of the bed/wall unit pairs resets its check-in message period 180 due to transmission of nurse call or bed exit signaling. Specifically, a collision between the check-in messages of two nearby bed units results in a bad CRC to either or both pairs of units. In this case, either or both bed units 14 in the two communications linlcs 22 receive a Nalc message from their corresponding wall units or do not receive any reply at all. This prompts the bed unit 14 to retry the transmission of the checlc-in message after a random delay. If the second transmission of the check-in message is successful, the bed unit 14 receives an Ack message fiom the wall unit 16 in response. The combination of first-try failure of the clleck-in sequence and first-resend success is a strong indication of colliding bed units 14 since other possible causes of packet corruption are not likely to appear and disappear quickly. Therefore, each bed unit 14 keeps a count of successive occurrences of the combination of successive first-try failures followed by first-resend successes.
If this count reaches a predetennined limit, such as 3 such combinations for example, the bed unit malces a permanent sliift in its nominal check-in message sequence time slot by adding a random delay to its next periodic check-in message transmission.

[0058] In response to detection of checlc-in message sequence collisions among inultiple cominunications linlcs 22, whether via detection of EOP byte corruption or via monitoring the described coinbination of successive first-try check-in message failures followed by first-resend successes, at least one of the bed/wall unit pairs whose communications link 22 is colliding initiates a change in its operating channel frequency to avoid future collisions.

[0059] Tuniing to Figure 13, should a coininuiiications link 22 fail or the responsible hospital persolmel forgets to link the two nearby bed and wall units 14, 16, one of the unlinked units sends out periodic link reminder messages to the other nearby unliiiked uiut(s) on each of the multiple operating channels and listens for corresponding acknowledgement (Ack) messages from one or more other unliiiked units. Preferably, the bed unit 14 sends out the luik reminder messages 200 - 206 on each of the system operating chaiulels and logs the wall IDs, or wall unit serial numbers, from wliich it receives acknowledgement replies 208 - 212 in the memory of its controller 100. Since the bed un.it 14 is battery operated where its transceiver circuitry 102 periodically enters an idle sleep mode, the bed unit includes a periodic reminder timer 216 to wake up its transceiver circuitry and begul the link reminder message cycle 220. In this embodiment, the system operates on 3 channels, therefore during each link reminder message cycle 220 the bed unit 14 transmits the link reminder messages 200 - 204 on each operating chamlel because the bed unit 14 is not aware of the current operating channel of a nearby unlinked wall unit. Transmission of link reminder messages on multiple operatiiig chaimels also talces into account possible collisions with other nearby bed units in the link reminder mode.
Pursuant to each transrnission of link reminder messages 200 - 206, the bed unit 141istens for incoming acknowledgement messages 208 - 212 for a coiTesponding listen period 214, which, in one einbodiment, is set to 100 milliseconds. Once the ful13 chamzel cycle 220 is coinplete, the bed unit resuines transmitting additional link reminder messages 206 during another link reminder message cycle 220, wlzich begins when the periodic reininder cycle 216 expires. In embodiments, the periodic relninder cycle 216 is set to 45 and 60 seconds, respectively. When the bed unit 14 detects a second aclaiowledginent message 212 originating from the saine wall ID or serial number as one of the previous aclrnowledginents 208, the bed unit 14 activates the link reminder alert 218 to proinpt the caregiver to initiate the liiAcing process.

[00601 Figures 14 - 19 illustrate the detailed operation of embodiments of various operating states of the system in accordance with the invention. Specifically, Figure 14 is a state diagrain generally illustrating the traiisition between various operational states of each bed/wall unit pair, while Figures 15 - 19 are flowcharts illustrating the operation of each of the states in Figure 14 in more detail. Figures 15 - 19 simultaneously depict operation of the bed and wall units by representing the steps associated with the bed unit on the left side, while representing the steps associated with the wall unit on the right side of eaclz figure. It should be noted that the steps referenced througliout Figures 15 -19 are perforined by progranunable firmware of each unit's controller 100, 114 (Figures 6 and 7).

[0061] As illustrated in Figure 14, after going through the linking process state 222, the linked bed/wall unit pair enters the linlced idle state 224 where the bed unit enters into the linked idle sleep mode by temporarily powering down its transceiver circuitry to extend the battery life wllen no patient information is transinitted, while the wall unit enters into a linlced idle receive mode to continuously listen for messages from one or more of its associated bed units. When the linked bed/wall unit pair needs to coininunicate patient infornnation, such as bed exit alairns or bed out calls, the w.lits enter the call message state 228 to relay the information to the nurse call system. Upon coinpletion of the call Inessage transmissions, the units reenter the linked idle state 224. Similarly, during periodic clieck-in message sequences, the linlced unit pair enters the checlc-iii message state 226 and retunis to the linlced idle state 224 when check-in message transmission is successful. However, when the cominunications linlc 22, 24 is lost or when the linking process fails, the bed and wall units enter the ui-Ainlced idle mode, which includes periodic link reminder alerts to prompt the health care provider to (re)establish the connnunications linlc 22, 24.

[0062] Turning to Figure 15, detailed operation of an embodiment of the linking process state 222 is illustrated, wllerein the bed unit initially powers down its transceiver circuitry in its unlinked idle sleep mode 232, while the wall unit is in the unlinked idle receive mode 234 for receiving link reminder messages from the bed unit. When the health care provider activates the bed unit's liiilc button, the bed unit begins transmitting linlc request (LRBC) messages for a predetennined duration, such as five (5) seconds, step 236. Similarly, in step 238, when the health care provider activates the wall unit's linlc button, the wall unit listens for the bed unit's link request messages for the five (5) second period. It should be noted that after transmitting a link request message, the bed unit switches to receive mode, for exainple for 70 milliseconds, to wait for an Ack message from a receiving wall unit, step 240. If, in step 242, the wall unit receives a linlc request message with good CRC, in step 244, the wall unit transmits an Ack with random delay to the bed unit and switches to receive mode for anotlier five seconds to wait for additional link requests from nearby bed units undergoing the liuiking process. As discussed above in connection with Figures 9-11, detection of additional bed/wall unit pairs simultaneously undergoing the linking process with the current pair, as well as the associated linlc failure, prevents unintended cross linking of the units located in adjacent rooms.
Alternatively, in step 246, when the wall unit receives a link request message with a CRC error, or, in step 248, when the wall unit does not receive any link request messages from the bed unit, the wall unit continues to listen, in step 250, for the bed unit's link requests for the duration of its link button activation timer 238.

[0063] Correspondingly, in step 252, wlien the bed iuiit receives a first Ack message from a given wall unit, it includes the associated wall ID or serial number in all subsequent link request messages, which the bed unit continues to send out on all operating chaimels for another five seconds. Alternatively, in step 254, the bed unit does not yet receive any aclcnowledgments from the nearby wall unit(s).

[0064] If, in step 256, the wall unit receives linlc request messages that include its ID or serial nw.nber in the destiuiation address field, it continues listening for liiik request messages originating from bed uiiit IDs other than the source of original link request message until the expiration of the linking period timer 244. Specifically, in step 258, if the wall unit receives a link request, containing its II) in the destination field, from a second bed unit ID designated as the source device, the link attempt irrunediately fails and the wall unit enters the unlinked idle receive mode, step 262, to prevent unintended cross linking of multiple bed/wall unit pairs.
Alternatively, in step 260, if the wall unit receives link request messages that do not contain its ID in the destination device field, the wall unit continues sending Ack messages until the 5 second linlcing period timer 244 expires. In step 264, at the end of the five second linking period tuner 244, the wall unit listens for an additional second for a link confirination message from the original bed unit and, in step 266, sends the corresponding acknowledgement message to establish the cominunications link and enters the linked idle receive mode, step 268. Otherwise, if the wall unit does not receive the final link confirmation message, step 270, the wall unit reenters the unlinked idle receive mode in step 272.

[0065] As with the wall unit, if, in step 274, the bed unit receives an Ack message from a second wall unit ID designated as the source device, the lii-dc atteinpt irnmediately fails and the bed unit enters an ui-Ainked idle sleep mode, step 276, to prevent unintended cross linlcing of inultiple bed/wall unit pairs. Otherwise, in step 278, the bed unit continuously transmits linlc request messages tl-iree (3) times on each of the operating channels until the expiration of the five (5) second timer 252. At the end of the five (5) second timer 252, the bed unit transmits a final link confirination message and awaits a corresponding Ack message from the wall unit, step 280.
To ensure successful coinpletion of the linking process, the bed unit is able to retry transmission of the fmal linlc confirmation message mitil it receives an acknowledgement from the wall unit.
Once the bed unit receives the acknowledgement to the link confirmation message, step 282, the bed unit enters the linked idle sleep mode in step 284 where it temporarily powers down its transceiver circuitry until either receiving patient iiiformation, such as bed out and bed exit alarms, or until the next periodic transinission of check-in messages.
Otherwise, in steps 286, 288, the bed unit enters the unlinked idle sleep mode where it initiates periodic linlc reminder messages and linlc reminder alerts to prompt the health care provider to reinitiate the linking process with a nearby unlinked wall unit.

[0066] Turning to Figure 16, detailed operation of an embodiment of the linked idle state 224 is illustrated. The bed/wall unit pair enters the linked idle state 224 after successful coinpletion of the linking process and pursuant to successfully relaying the patient inforination between the units, including the nurse call signaling initiated by the patient, bed exit and bed out alanns, as well as periodic check-in or liiAc status message transmissions, steps 290 -300. In this case, the bed unit remains in a linlced idle sleep mode 302 wlierein it temporarily powers down its transceiver circuitry until it is time to transmit periodic checlc-in messages to the wall unit, steps 304, 306, or the bed unit needs to relay the patient information to the wall unit, for exainple when the bed unit detects that the patient activated a nurse call button via the siderail communications module, steps 308, 310.

[0067] Correspondingly, the wall unit remains in the idle receive mode 312 where it listens for bed unit transmissions and subsequently enters the checlc-in message state, steps 314, 316, or the call message state, steps 318, 320, upon receipt of periodic check-in messages or other patient information from the wall unit. It sliould be noted that, in step 322, the wall unit monitors noise on its operating channel in order to detect and evade interference from other bed/wall units, as well as fi-oln other devices occupying the same spectrum, such as cordless phones operating in Direct Sequence Spread Spectrum mode, for exainple.
Therefore, in this embodiment, if the wall uiiit detects noise after a few consecutive noise readings, it moves to the next operating channel and switches to receive mode, while waiting for the linked bed unit to attempt a new transinission, accuinulate a plurality of Missed Wall Unit events, and rejoin the wall unit on the new channel. Finally, when the health care provider activates the unlink button at either unit, the bed unit enters the unliiAced idle sleep mode, where it periodically wakes up its transceiver circuitry to send out the link reminder messages to nearby unliiilced wall units, while the wall unit enters the uiilinlced idle receive mode to listen for the bed unit's link reminder transmissions, steps 324 - 330.

[0068] Turning to Figure 17, detailed operation of an embodiment of the check-in message state 226 is illustrated. In this embodiment, when the linked bed/wall units are in their respective l'ullced idle znodes, steps 332, 334, the bed unit periodically transmits check-in, or lil-Ac status, messages to the associated wall unit and teinporarily switches to receive mode in order to await for corresponding acknowledginents from the wall unit, steps 336, 338. In aii embod'unent, the bed unit periodically transmits the check-in messages every 45 seconds and thereafter switches to the receive mode for a 701nillisecond duration.

[0069] If the wall unit receives a check-in message with good CRC value, the wall unit transmits an Ack message and, in this embodiment, listens for another 200 milliseconds for any incoming retry transmissions from the bed uiiit prior to coinpleting the check-in process by returning to the l'uilced idle receive mode until the onset of the next check-in message period in 45 seconds, steps 340 - 344. Alternatively, if the wall unit receives a check-in message having a CRC error, the wall unit replies with a Nak message and listens for subsequent retry transmissions by the bed unit, steps 346, 348. In yet another scenario, if the wall unit does not yet receive the check-in message, whether due to poor RF conditions or otherwise, the wall unit remains in the linked idle receive mode to await the incoming check-in message transmission, step 350. During the check-in message state, the wall unit also monitors the current channel for noise conditions and, upon detecting presence of RF noise, the wall unit changes the operating frequency, step 352.

[0070] Wlien the bed unit receives an Ack message indicating successful receipt of the check-in message by the wall unit, the bed unit returns to the linked idle sleep mode until the next check-in message period, steps 354, 356. Alternatively, if the bed unit receives a Nak message from the wall unit, indicating a CRC eiTor in a check-in message received by the wall unit, the bed unit retries the transinission of the check-in message after a random delay after the receipt of the Nak message and awaits for a successful acknowledgement, steps 358, 360.
Further, if the bed lmit does not receive any reply messages from the wall unit, the bed uiiit retries transmitting another check-in message and listens for wall unit's replies, steps 362, 364.
[0071] In this embodiment, upon transinitting three (3) consecutive acknowledgements to the same bed unit witliin the check-in period, the wall unit changes to anotller operating channel, step 366, since repeated retries of check-in message transmission by the bed unit indicate a reception problem at the bed iuiit. Similarly, if the bed unit transinits three (3) consecutive check-in message retries witliout receiving an Ack from the wall unit, the bed unit changes to another operating channel to retry the transmission since the wall unit already moved to a different chamiel after transmitting three (3) consecutive Ack messages missed by the bed unit, step 368. Signal degradation at the wall unit is the likely reason for the wall unit transmitting 3 consecutive Nak messages to the saine bed unit within the saine check-in message period without receiving a check-in message with a good CRC value. In this case, the wall unit moves to another operatulg channel and switches to receive mode to listen for check-in messages from the bed uiiit once it follows the wall unit to the new channel, step 370. The wall unit also moves to another chaimel if it is overdue for receiving the next periodic check-in message transmission, such as when the periodic check-in timer has expired by two (2) seconds, step 371.

[0072] In step 372, the bed unit receives 3 consecutive Nak messages and follows the wall unit by moving to another one of the operating channels to retry the transmission of check-in inessages. The bed unit repeats transmission on each new channel until it finds the wall unit's channel by receiving an acla7owledginent message. Otherwise, the bed unit retries transmitting the check-in messages on different channels until some predetermined time from last receiving an Ack message. In one einbodiment, the cominunications link fails and the bed unit enters the unlinked idle sleep mode when 60 seconds elapse from receipt of the last Ack message, steps 374, 376. Similarly, the wall unit listens for bed unit's check-in messages for one (1) second on each of the operating cham-lels until the expiration of the one minute tiiner.
Tilereafter, the wall unit enters the unlinlced idle receive mode, steps 378, 380.

[0073] As discussed above in connection with Figure 12, to provide for early detection of clleck-in message collisions between check-in message sequences of multiple bed/wall unit pairs and prevent data coiTuption, the bed unit shi$s its nominal time slot for periodic transmission of check-in messages by adding a random delay to the next scheduled check-in message transmission wlzen it detects corruption of the end-of-packet byte in acknowledgement messages having good CRC values, step 382. Additionally, the bed unit shifts its noininal time slot for transmission of periodic clieck-in messages by monitoring for successive occurrences of check-in message retries followed by successful receipt of Ack messages. This method of check-in message time slot management detects a sudden and recurring collision of clleck-in message sequences, which occur after one of the bed/wall unit pairs resets its check-in message timer due to transmission of nurse call or bed exit signaling. In this embodiment, if the bed unit receives 3 consecutive Ack messages in response to three (3) consecutive retries of check-in message transmissions, the bed unit similarly shifts its nominal check-in message time slot by adding a random delay to the next periodic check-in message transinission time, step 384.

[0074] Turning to Figure 18, detailed operation of an embodiment of the call message state 228 is illustrated. In the illustrated embodiment, the linked bed/wall unit pair relays patient-initiated nurse call signaling to the hospital nurse call system, however it should be understood that the following steps also apply to transinission of other patient infonnation, including bed out and bed exit alerts. While the linked bed/wall unit pair is in the linlced'idle mode, steps 386, 388, the bed unit detects activation of the nurse call button and transmits the nurse call message to the associated wall unit, steps 390, 392.

[0075] If the wall unit receives the nurse call signal with good CRC, the wall unit places a call on the nurse call system, transmits an Ack message, and listens for another 200 milliseconds for any incoming retry transmissions from the bed unit in case the bed unit does not receive the Ack message due to a signal reception problem, steps 394, 396. If the wall unit does not receive a retry transinission from the bed unit, the wall unit coinpletes the transmission process by retunzing to the linked idle receive mode, steps 398. Alteniatively, if the wall unit receives a nurse call message having a CRC error, the wall unit replies with a Nak message and listens for subsequent retry transmissions by the bed unit, steps 400, 402. If, however, the wall unit does not yet receive any message, whether due to poor RF conditions or otherwise, the wall unit remains in the linked idle receive mode, step 404. While in the call message state, the wall unit also monitors the current channel for noise conditions and, upon detecting presence of RF noise, changes the operating frequency, step 406.

[0076] When the bed unit receives an Ack message, the bed uiiit retu.rns to the linked idle sleep mode until either the next check-in message period or the next transmission of patient uzformation between the linked units, steps 408, 410. Alternatively, if the bed uiiit receives a Nak message from the wall unit, indicating a CRC error, the bed unit retries the transmission of the nurse call message with a randoln delay after the receipt of the Nak message and awaits for a successful acknowledgement, steps 412, 414. Furtlier, if the bed unit does not receive any reply messages from the wall unit, the bed unit retries transmitting another nurse call message and listens for the wall unit's replies, steps 416, 418.

[0077] Upon transmitting three (3) consecutive aclcnowledgements to the bed unit, the wall unit changes to another operating chamlel, step 420, since repeated retries by the bed unit indicate that it is having a reception problem. Similarly, if the bed unit transmits three (3) consecutive retries without receiving an Ack from the wall unit, the bed unit changes to another operating channel since the wall unit already moved to a different chaiinel after transmitting three (3) consecutive Ack messages missed by the bed wzit, step 422. Signal degradation at the wall unit is the likely reason for the wall unit transmitting three (3) consecutive Nalc messages to the saine bed unit without receiving a message with a good CRC value. In this case, the wall unit moves to another operating channel and switches to receive mode to listen for retry inessages from the bed unit when it follows the wall unit to the new channel, step 424. Thus, in step 426, the bed unit follows the wall unit when it receives three (3) consecutive Nak messages and moves to another one of the operating channels to retry the transmission.
The bed unit repeats transinission on each new channel until it fmds the wall unit's channel by receiving an aclazowledgment message. Otherwise, the bed unit retries transmitting the messages on different channels until some predetennined time from last receiving an Ack message. In one embodiment, the coininunications link fails and the bed unit enters the unlinked idle sleep mode wlien 60 seconds elapse from receipt of the last Ack message, steps 428, 430.
Similarly, the wall unit listens for the bed unit's message for one (1) second on each of the operating channels until the expiration of the one minute timer. Thereafter, the wall unit enters the unlinked idle receive mode, steps 432, 434.

[0078] Turning to Figure 19, detailed operation of an einbodiment of the unlinked idle state 230 is illustrated. The bed and wall units enter the unluilced idle state either due to failure of the coinmunications linlc between a bed/wall unit pair, failure of the linking process, or when the health care provider activates the unlinic button on one of the units, steps 436 - 446. While in the unlinked idle sleep mode,, the bed unit completes periodic link relninder cycles, wlierein it sends out a link reminder message on each of the operating chamlels and waits for acknowledgments from nearby unlinked wall units, steps 448, 450. Since an unlinked bed unit is not aware of the nearby wall unit's current operating chaimel, the bed unit repeats the 1h-iic reminder cycle on each operating channel after a predetennined period. In embodiments, the bed unit repeats the link reminder cycle every 45 or 60 seconds. When the wall unit receives the liiik reminder message witli correct CRC value, it responds with an Ack message, steps 452, 454.
Alternatively, if the wall unit receives a link reminder message witli a CRC error, or when the wall Luiit does not yet receive any link reminder messages, the wall unit remains in the idle receive mode, steps 456 -460. While in the idle receive mode, the wall unit scans the current channel for noise and moves to another operatuig channel if it detects interference from nearby bed or wall units and/or other devices sharing its spectrum, step 462.

[0079] Upon receipt of the Ack messages from one or more nearby unlinked wall units, the bed unit logs each wall unit's unique identifier, which in this einbodiment is the device serial number, in a list of wall IDs, step 464. If the bed unit is not in vicinity of an unlinked wall unit, it does not receive any Acks, step 466. After logging the wall IDs associated with the incoming Ack messages for 100 milliseconds, the bed unit moves to another channel to transinit the next link reminder message, step 468. If, in steps 470 - 476, the caregiver decides to activate the units' respective linlc buttons, both uiiits transition to the linking process state 222. In steps 478, 480, the wall unit continues to respond witli acknowledgement messages upon receipt of link reminders with correct CRC values. Otherwise, in step 482, the wall unit remains in the idle receive mode. When the bed unit receives two consecutive acknowledgments from the wall ID
that is already on its wall ID list 464, the bed unit activates a link reminder alert to prompt the llealth care provider to initiate the linking process of the two nearby units, step 484. In this embodiment, the linlc reminder alert is an audio alarm, such as a short chirp.
Other embodiments include using visual alerts, such as flashing one or more LEDs. If the health care provider wishes to deactivate the linlc reminder alert, the healtll care provider activates the bed unit's unlinlc button, which moves the list of wall IDs to a silence list for a predeterinined duration, such as one hour, step 486. Consequently, the bed unit does not sound the link remuider alert if it subsequently receives acknowledgements from wall unit IDs already on the silent list, step 488.

[0080] All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.
[0081] The use of the terms "a" and "an" and "the" and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover botli the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms "coinprising," "liaving," "including," and "containing"
are to be construed as open-ended terms (i.e., meaning "including, but not limited to,") uiiless otlierwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of refeiTing individually to each separate value falling within the range, unless otherwise uidicated herein, and each separate value is incoiporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., "such as") provided herein, is intended merely to better illuminate the invention and does not pose a liinitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

[0082] PrefeiTed embodiments of this uzvention are described hereui, including the best mode lalown to the inventors for caiTying out the invention. Variations of those prefeiTed embodiments may becoine apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to einploy such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.

Claims

1. A method for establishing a wireless communications link between a pair of medical communications devices, wherein the pair is associated with a mobile hospital bed for relaying patient information to a health care provider, the method comprising:

requesting creation of the wireless communications link in response to a user input at a first medical communications device of the pair;

responding to the request if a user input occurs at a second medical communications device of the pair within a predetermined amount of time after making the request; and failing to establish the wireless communications link upon detecting an attempt to create the link by a third medical communications device, wherein the attempt is detected prior to establishing the link.

2. The method of claim 1 wherein the wireless communications link between the pair of medical communications devices is a first communications link and the pair is a first pair, the method further comprising establishing a second communications link between a second pair of medical communications devices, wherein the second pair includes one of the medical communications devices of the first pair.

3. The method of claim 1 wherein the user inputs at the first and second medical communications devices includes pressing a button at each of the medical communications devices within the predetermined amount of time.

4. The method of claim 1 wherein the first and second medical communications devices exchange unique addresses identifying the devices in order to establish the wireless communications link.

5. The method of claim 4 wherein exchanging the unique addresses further comprises exchanging device serial numbers.

6. The method of claim 1 wherein at least one of the first and second medical communications devices reduces power consumption after establishing the wireless communications link.

7. The method of claim 6 wherein the other of the first and second medical communications devices remains fully powered after establishing the wireless communications link.

8. The method of claim 1 wherein the patient information includes at least one of a patient occupancy status signal associated with the mobile hospital bed, a nurse call signal, a call assurance signal, and a system status signal associated with at least one of the devices within the pair.

9. A network for establishing a wireless communications link between a pair of medical communications transceivers, the network comprising:

a first transceiver attached to a mobile hospital bed for relaying patient information to a second transceiver separated from the mobile hospital bed, the second transceiver communicating the patient information to a health care provider;

one of the transceivers including a transmitter for requesting establishment of the wireless communications link between the pair of transceivers; and at least one of the transceivers including a receiver for failing to establish the communications link upon detecting an attempt to establish a different wireless communications link for relaying the patient information.

10. The network of claim 9 wherein the wireless communications link between the pair of medical communications transceivers is a first communications link and the pair is a first pair, the network further comprising a third medical communications transceiver for establishing a second communications link between a second pair of medical communications transceivers, wherein the second pair includes the third medical communications transceiver and one of the medical communications transceivers of the first pair.

11. The network of claim 9 wherein the second transceiver communicates the patient information to the health care provider through a hospital communications network for monitoring the patient information.

12. The network of claim 9 including a user interface associated with the transmitter for initiating the request to establish the wireless communications link in response to a user input at the user interface.

13. The network of claim 12 including a user interface associated with the at least one receiver for initiating a response to a user input at the user interface, said response being received within a predetermined amount of time after the request for establishing the link in order for the link to be successfully established.

14. The network of claim 9 wherein the patient information includes at least one of a patient occupancy status signal associated with the mobile hospital bed, a nurse call signal, a call assurance signal, and a system status signal associated with at least one of the devices within the pair.

15. A medical communications device for wirelessly relaying patient information from a mobile hospital apparatus to a fixed site, the medical communications device comprising:

a housing secured to the mobile hospital apparatus;
a user interface for receiving user inputs;

a transceiver for supporting the wireless communications link with the fixed site;

a controller connected to the user interface and the transceiver for cooperating with the fixed site in order to (1) initiate an attempt at establishing the wireless communications link in response to a user input and (2) fail completion of the link when the attempt to establish the link overlaps an attempt to establish another link originating from a source other than either the device or the fixed site.

16. The medical communications device of claim 15 wherein the wireless communications link between the device and the fixed site is a first communications link and wherein the fixed site establishes a second communications link with the source of the attempt to establish the other link.

17. The medical communications device of claim 15 wherein the controller includes timing circuitry requiring receipt of one or more user inputs within a predetermined amount of time after the attempt to establish the wireless communications link in order to successfully establish the link.

18. The medical communications device of claim 15 wherein the fixed site is associated with a hospital communications network for communicating the patient information to a health care provider.

19. The medical communications device of claim 15 wherein the patient information includes at least one of a patient occupancy status signal associated with the mobile hospital apparatus, a nurse call signal, a call assurance signal, a system status signal associated with at least one of the medical communications device and the fixed site.

20. A fixed medical communications device for communicating patient information between the device and a mobile unit via a wireless communications link, where the mobile unit is associated with a hospital apparatus, the fixed medical communications device comprising:

a user interface for receiving user inputs;

a transceiver supporting the wireless communications link with the mobile unit; and a controller connected to the user interface and the transceiver for cooperating with the mobile unit in order to (1) initiate an attempt at establishing the wireless communications link in response to a user input and (2) fail completion of the link when the attempt to establish the link overlaps an attempt to establish another link originating from a source other than either the fixed medical communications device or the mobile unit.

21. The fixed medical communications device of claim 20 wherein the wireless communications link between the fixed medical communications device and the mobile unit is a first communications link and wherein the fixed medical communications device establishes a second communications link with the source of the attempt to establish the other link.

22. The fixed medical communications device of claim 20 wherein the device communicates the patient information to a health care provider through a hospital communications network for monitoring the patient information.

23. The fixed medical communications device of claim 20 wherein the controller includes timing circuitry requiring receipt of one or more user inputs within a predetermined amount of time after the attempt to establish the wireless communications link in order to successfully establish the link.

24. The fixed medical communications device of claim 20 wherein the patient information includes at least one of a patient occupancy status signal associated with the hospital apparatus, a nurse call signal, a call assurance signal, and a system status signal associated with at least one of the fixed medical communications device and the mobile unit.

25. A method for maintaining a wireless communications link between a mobile unit gathering patient information and a stationary unit for processing the patient information, the method comprising:

repeatedly transmitting link status messages between the mobile and stationary units;
monitoring the link status messages for collisions with other communications links; and shifting subsequent transmissions of the link status messages when a collision is detected.

26. The method of claim 25 further comprising one of shifting a time reference of the subsequent transmissions of the link status messages and transmitting the link status messages on another operating channel when the collision is detected.

27. The method of claim 25 wherein the collision is detected prior to corruption of data fields in the link status messages.

28. The method of claim 27 wherein the collision is detected by monitoring a collision indicator field in the link status messages.

29. The method of claim 25 further comprising retrying the transmission of the link status messages on another operating channel when the wireless communications link is impaired due to a degradation in signal conditions.

30. The method of claim 25 further comprising routing the link status messages based on unique identifiers corresponding to each of the mobile and stationary units.

31. The method of claim 25 wherein the wireless communications link supports a message format for relaying the patient information to a hospital communications network and the link status messages include full frame transmissions according to the message format.

32. The method of claim 25 wherein the patient information includes at least one of a bed occupancy status signal, a nurse call signal, a nurse call assurance signal, a wireless communications link status signal, and an operating status signal associated with at least one of the units.

33. A method for maintaining wireless communications links, each link communicating patient information between a portable device attached to a portable hospital resource and a stationary device, the method comprising:

repeatedly transmitting link status messages over two or more of the wireless communications links, where the transmissions by each link are periodic;

detecting a collision between the two or more wireless communications links transmitting the link status messages, wlierein the collision occurs due to a temporal overlap of the link status messages of the two or more wireless communications links;
and shifting the repetition of the periodic link status messages in at least one of the wireless communications links when the collision is detected.

34. The method of claim 33 further comprising one of shifting a time reference of the repetition of the periodic link status messages and transmitting the link status messages on another operating channel when the collision is detected.

35. The method of claim 33 wherein the collision is detected prior to data corruption by monitoring a collision indicator field in the link status messages.

36. The method of claim 33 further comprising retrying the transmission of the link status messages on another operating channel for at least one of the wireless communications links when the at least one wireless communications link is impaired due to a degradation in signal conditions.

37. The method of claim 33 wherein the wireless communications links support a message format for relaying the patient information to a hospital communications network and the link status messages include full frame transmissions according to the message format.

38. The method of claim 33 wherein the patient information includes at least one of an occupancy status signal associated with the portable hospital resource, a nurse call signal, a nurse call assurance signal, a wireless communications link status signal, and an operating status signal associated with at least one of the devices.

39. A system for maintaining a wireless communications link between a mobile hospital bed and a hospital communications network, the system comprising:

a pair of transceivers supporting a wireless communications link between the mobile hospital bed and the hospital communications network;

one of the transceivers including an interface that enables the transceiver to function as a node of the hospital communications network; and the other transceiver including a mechanical connector for fastening the transceiver to the mobile hospital bed and circuitry for (1) repeatedly transmitting to the one transceiver link status messages, (2) detecting a collision of at least one of the link status messages with other communication links and (3) shifting transmissions of the link status messages subsequent to detection of the collision.

40. The system of claim 39 wherein the other transceiver further includes circuitry for one of shifting a time reference of the transmissions of the link status messages and transmitting the link status messages on another operating channel when the collision is detected.

41. The system of claim 39 wherein the collision is detected prior to data corruption by monitoring a collision indicator field in the link status messages.

42. The system of claim 39 wherein the other transceiver further includes circuitry for retrying the transmission of the link status messages on another operating channel when the wireless communications link is impaired due to a degradation in signal conditions.

43. The system of claim 39 wherein the transceivers route the link status messages based on a unique identifier corresponding to each transceiver.

44. The system of claim 39 wherein the wireless communications link supports a message format for relaying the patient information to the hospital communications network and the link status messages include full frame transmissions according to the message format.

45. The system of claim 39 wherein the wireless communications link relays patient information to the hospital communications network, the patient information including at least one of a patient occupancy status signal associated with the mobile hospital bed, a nurse call signal, a call assurance signal, and a system status signal associated with at least one of the transceivers.

46. A mobile medical communications device for relaying patient information via a wireless communications link to a stationary site, the device comprising:

a transceiver for establishing a wireless communications link to the stationary site, where the wireless communications link supports a message format for relaying patient information to the stationary site;

a controller in communication with the transceiver and a source of patient information for (1) causing the transceiver to repeatedly transmit link status messages to the stationary site, thereby checking an integrity of the wireless communications link, and (2) shifting the repeatedly transmitted link status messages upon detection of corruption of at least one of the link status messages; and a housing for the transceiver and controller that includes a fastener for mechanically attaching the housing to a portable hospital resource.

47. The mobile medical communications device of claim 46 wherein the controller causes the transceiver one of to shift a time reference of the transmissions of the link status messages and to transmit the link status messages on another operating channel when the collision is detected.

48. The mobile medical communications device of claim 46 wherein the corruption is detected prior to losing data by monitoring a collision indicator field in the link status messages.

49. The mobile medical communications device of claim 46 wherein the controller causes the transceiver to retry the transmission of the link status messages on another operating channel when the wireless communications link is impaired due to a degradation in signal conditions.

50. The mobile medical communications device of claim 46 wherein the link status messages are routed between the mobile medical communications device and the stationary site based on their respective unique identifiers.

51. The mobile medical communications device of claim 46 wherein the link status messages include full frame transmissions according to the message format.

52. The mobile medical communications device of claim 46 wherein the patient information includes at least one of a patient occupancy status signal associated with the portable hospital resource, a nurse call signal, a call assurance signal, and a system status signal associated with at least one of the mobile medical communications device and the stationary site.

53. A stationary medical communications device for receiving patient information from a mobile telecommunications device attached to a portable hospital resource, the stationary medical communications device comprising:

a transceiver establishing a wireless communications link with the mobile telecommunications device; and a controller in communication with the transceiver for detecting corruption of one or more link status messages repeatedly transmitted by the mobile telecommunications device, and providing an indication that subsequent transmissions of the link status messages should be shifted to avoid future corruption.

54. The stationary medical communications device of claim 53 wherein in response to the indication the mobile telecommunications device changes one of a time reference and an operating channel of the subsequent transmissions of the link status messages.

55. The stationary medical communications device of claim 53 wherein the controller provides a further indication to retry the transmission of the link status messages on another operating channel when the wireless communications link is impaired due to a degradation in signal conditions.

56. The stationary medical communications device of claim 53 wherein the link status messages are routed between the stationary medical communications device and the mobile telecommunications device based on their respective unique identifiers.

57. The stationary medical communications device of claim 53 wherein the wireless communications link supports a message format for relaying the patient information to a hospital communications network and the link status messages include full frame transmissions according to the message format.

58. The stationary medical communications device of claim 53 wherein the patient information includes at least one of a patient occupancy status signal associated with the portable hospital resource, a nurse call signal, a call assurance signal, and a system status signal associated with at least one of the mobile telecommunications device and the stationary medical communications device.

59. A method for alerting personnel to establish a communications link between a mobile hospital apparatus and a stationary point, the method comprising:

transmitting a link reminder message between the mobile hospital apparatus and the stationary point;

transmitting a link response message in response to the link reminder message;
and signaling the personnel after transmission of the link reminder and link response messages that the communications link between the mobile hospital apparatus and the stationary point is not established.

60. The method of claim 59 further comprising periodically transmitting the link reminder message.

61. The method of claim 59 further comprising transmitting the link reminder message on a plurality of operating channels.

62. The method of claim 59 wherein the signaling of the personnel occurs after two or more pairs of transmissions of the link reminder and link response messages.

63. The method of claim 59 wherein the transmission of the link reminder and link response messages is wireless.

64. A system for reminding personnel to establish a wireless communications link between a pair of transceivers, the system comprising:

a first transceiver for generating one or more signals indicating it is available for establishing the wireless communications link with another device;

a second transceiver responsive to the signals from the first transceiver for generating complementary signals indicating the second transceiver is available for establishing the wireless communications link; and a signaling device for alerting the personnel that the first and second transceivers are available for establishing the wireless communications link.

65. The system of claim 64 wherein one of the first and second transceivers is attached to a mobile hospital bed for relaying patient information to the other of the first and second transceivers.

66. The system of claim 65 wherein the other of the first and second transceivers is connected to a hospital communications network for monitoring patient information received from the one of the first and second transceivers.

67. The system of claim 64 wherein the signaling device for alerting the personnel comprises at least one of an audio signaling device, and a visual signaling device.

68. The system of claim 67 wherein the signaling device shares a common housing with one of the first and second transceivers and the housing includes a fastener for attaching the signaling device and the one of the first and second transceivers to a mobile hospital apparatus.

69. A medical communications device in a pair of devices for transmitting patient information via a wireless communications link, the medical communications device comprising:
a user interface for receiving user inputs;

a transceiver for establishing the wireless communications link with another device forming the pair of devices for transmitting the patient information; and a controller responsive to the transceiver for detecting a presence of the other device in the pair; and a signal generator responsive to the controller for prompting action by personnel responsible for establishing the wireless communications link.

70. The medical communications device of claim 69 wherein the medical communications device is attached to a mobile hospital bed for transmitting the patient information to the other device, said other device installed within a hospital facility.

71. The medical communications device of claim 70 wherein the other device is connected to a hospital communications network for monitoring the patient information.

72. The medical communications device of claim 69 wherein the signal generator comprises at least one of an audio signaling device, and a visual signaling device.

73. The medical communications device of claim 70 wherein the patient information includes at least one of a patient occupancy status signal associated with the mobile hospital bed, a nurse call signal, a call assurance signal, and a system status signal associated with at least one of the devices within the pair.

74. A medical communications device in a pair of devices for transmitting patient information via a wireless communications link between a hospital bed and a stationary base, the medical communications device comprising:

a user interface for receiving user inputs;

a transceiver for establishing the wireless communications link with another device in the pair of devices for transmitting the patient information between the hospital bed and the stationary base;

a controller responsive to the transceiver for detecting a presence of the other device in the pair and informing the other device that the transceiver is available for establishing the wireless communications link such that an alerting signal prompts action by personnel responsible for establishing the wireless communications link.

75. The medical communications device of claim 74 wherein the medical communications device is installed within a hospital facility for receiving the patient information from the other device in the pair, said other device in the pair attached to the hospital bed.

76. The medical communications device of claim 74 wherein the stationary base is connected to a hospital communications network that receives the patient information.

77. The medical communications device of claim 74 wherein the alerting signal comprises at least one of an audio signal, and a visual signal.

78. The medical communications device of claim 77 wherein the alerting signal is housed with the other device.

79. The medical communications device of claim 74 wherein the patient information includes at least one of a patient occupancy status signal associated with the hospital bed, a nurse call signal, a call assurance signal, and a system status signal associated with at least one of the devices within the pair.