TWP Wireless

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TWP Wireless Communication System

TWP Communication System keeps all the best features of regular POCSAG and FLEX one-way paging – small size, low cost, very easy to use and so on. In the same time two-way communication technology creates many advantages.

Reliability. The biggest advantage of this new system is the extraordinary communication reliability. There are several areas of improvement.

·        For every transmitted communication message there is a conformation message that is generated automatically by the receiver. The sender is warned immediately (!) in case a message cannot be delivered by any reason.

·        There is no any unique component (like the transmitter in a one-way paging system) whose health is vital for the whole system.

·        Extra repeaters can be easily deployed to get assurance that two or more repeaters redundantly cover every spot of communication area.

·        There is no “central computer” any more. The communication devices (including computers) send messages to each other directly or through the net of repeaters.

·        All the components of the system are under permanent self- and cross-examination. Any recognized problem is immediately reported to the user or to the system administrator.

·        Escalation procedure is used for the warning messages. For example: if a user of a pager ignores the “low battery “ warning for a long time, an appropriate message will be finally send to the system administrator.

·        Most of repeaters have incorporated battery backup that helps keep system alive for several weeks without external power supply.

New Communication Possibilities. Now the user of a pager can send back a response to the message received immediately using the pager keyboard or a wireless keyboard.

In contrast to public paging service, the on-site system does not require access fee, it has much higher transmission speed and does not have blind spots! User has reliable communication level even in underground garages or deep basements!

FCC. As a result of the fact that this system is based on ISM transceiver, the user does not need any license from FCC to install it. Several such systems can coexist in the overlapping areas without any disturbance.

Communication Standard. TWP Communication System is compatible with ZigBee technology. ZigBee is a wireless control network protocol used for home, building and industrial control. It conforms to the IEEE 802.15.4 wireless standard for low data rate networks. With a maximum speed of 250 Kbps at 2.4GHz, TWP Communication System is slower than Wi-Fi and Bluetooth, but it is designed for low power so that batteries can last for months and years. In the same time it is a 100 times faster than POCSAG or FLEX. Like ZigBee, our system  uses two types of devices. Reduced-function devices (RFDs) are peripheral units that communicate with full-function devices (FFDs). FFDs are complex nodes that conform to the full 802.15.4 standard and can serve as routers. As routers and peripheral units are integrated into a network, they obtain information about the network from the coordinator or from any router that already has joined. This information lets other devices set their operational parameters to reflect those of the network, and so join it.

Simple on-site two-way messaging system consists of peripheral units (TWP Communicators) and routers. TWP Communicator looks like a regular one-way alphanumeric pager. It has all the pager parts (keys, display, battery, buzzer, vibrator and so on) and a micro-power transceiver inside. It sends and receives messages through a router. All received messages are stored in the Communicator memory. User can respond to a message by sending back one of preprogrammed answer or one of answers attached to the message.

The most popular full-function device is a Computer Gate. Computer Gate can be connected to a computer or any other device that has a RS232 or USB port. It is powered from the port that it connected to. It has also batteries on board so it can operate for several days as a router even when computer is shut down.

There are three other popular forms of ZigBee Units. The first of them is an Alarm Unit. This unit can be programmed to send a specific message in case a key is pushed. The big advantage of ZigBee based alarm unit is the inherited escalation procedure. Several messages can be programmed in one unit. If the first message cannot be delivered or the message recipient not respond in predefined time, another message is activated. When the recipient responds to the message, the alarm unit vibrator informs the sender that help is on the way.

 The second special type of ZigBee Unit is a Wireless Keyboard. It looks like regular PC keyboard (but without cable) and can be used with any TWP Communicator to create a message.

The third popular form of ZigBee Unit is a Power Control Unit. Power Control Unit has high current relay on board that is controlled remotely by special messages. This unit can be used to control wide range of electrically powered devices. Since this unit is permanently connected to a power, it can operate as a router.

Router with two AA size rechargeable batteries can work for several days without external power supply. Each router covers up to 200-foot diameter area and can support hundreds of pagers within this area. More routers can be added to enlarge the covered area or to improve the service in crowded spots.  When a TWP Communicator has a message to send, it actually sends a data package to nearby router. Data package has information about recipient (Recipient Name) and text of message. Router analyses Recipient Name and sends the message to recipient directly or through other routers (in case the recipient is too far).

Transmitting message from one router to another creates delay in message delivery. For large area this delay can be as long as several seconds. In order to reduce this time accelerators can be used. An accelerator is in fact a router (Computer Gate, Ethernet Gate and so on) that is connected to another accelerator directly by some kind of wire (twisted pair, coaxial cable), through a LAN or through Internet.  Accelerators are also used when covered area consists of several separated spots (for example: main office in downtown and warehouse in industrial park).

A router is the only element that is required to send a message from one unit to another. In order to connect a system to external world a Gate can be added. A Gate is a unit that has appropriate interface (hardware and software) to send and receive messages from external sources such as computer, phone line, Nurse Call Ssystem, LAN, Internet and so on.

Some applications need information about position of a Communicator (alarm unit) within covered area. In this case the Beacons are used. Beacons transmit special signals that create geographical values for peripheral units to discover theirs coordinates.

 The key feature of our communication system is reliability. When user sends a message, he or she knows for sure that message was delivered successfully. If message cannot be delivered the sender will be warned immediately. Routers communicate to Communicators, to each other and to other elements of a system using TWP Wireless Control and Monitoring Protocol.

 TWP Wireless Control and Monitoring Protocol is based on ZigBee and designed especially for overcrowded environment. It can monitor and support up to 64,000 units in one system. This self-adjustment protocol makes the system very friendly and extremely reliable. Malfunction or even death of any element of the system does not reduce critically the performance of whole system. Usually the computer stability is vital for a computer-controlled paging system. Computer virus or hardware fault could break down the whole system, but not in our case. TWP Wireless Control and Monitoring Protocol does all the synchronization, registration and transportation work, checks the presence and the functioning of all elements of the system and creates appropriate warning message in the case of any alarmed situation. Every element of the whole system (communicator, router, beacon, accelerator, gate) does its part of Protocol. This very powerful system does not need a computer at all!

 How it works: every element of the system (pager, router, beacon and so on) has a descriptor and a unique Device ID. This ID consists of thee parts - manufacturer, type of device and serial number. Descriptor keeps specific information about device (display size, number of keys, maximum message length and so on). All this information is programmed by manufacturer and cannot be changed. The System uses this information during subscription stage. Every system has its own unique System ID. Usually it is the Device ID of the first router of the system. Subscription is mandatory step to add new element to the system. Administrator only has right to subscribe or unsubscribe a device to the System. Information about the subscription (System ID) is stored in device internal memory. After a device is subscribed to one system it cannot be subscribed and used in another system. During subscription process a devise gets a name that is unique for this system (for example “Peter Brown” or “5001”). This name is used to send messages to this device (pager). During the subscription procedure a new device receives all the information about system settings, set of preprogrammed answers, administrator’s Unit ID etc. Being very complicated internally this procedure however is highly automated. All administrator has to do is to answer some questions about features that are new to this system. If one device is programmed, all other devices of the same type can be “cloned” i.e. programmed with the same settings (but with unique names, of course). Another vital step is registration. Every time a peripheral unit goes out of covered area and returns back it has to go through the registration process. During the process of registration a unit communicate to the closest router and sends it’s subscription information. If this information is correct the device gets permission to communicate to the system. It is Subscription/Registration duo that makes security of the system very high. There is no way to send or receive message through not permitted device. One more very important feature of this System is an upgrading procedure. Administrator starts the upgrading procedure when part of subscription information has to be changed in all or several units. If some unit appeared to be outside of covered area during the upgrading, it will be upgraded automatically during its next registration. In case of any problem with the message traffic or if some information about the system health is required, the statistic procedure can be used. When statistic is activated the routers accumulate all the required information about delays, number of messages in input/output buffers and so on.

Self-testing. After a unit (pager, router) successfully passed the registration procedure, the system checks the presence and health of every unit periodically (up to 1 time per second). All the elements of a system are always under permanent monitoring! In case of any problem the system generates and sends to administrator a warning message that describes the problem, the unit name and its location.

Message handling. When a peripheral device (pager) sends a message to another device it receives back from the system a conformation or a warning that the recipient is out of area. There are two different methods of message transmitting: asynchronous (“posting”) and synchronous (“sending”). When a Communicator “posts” a message to another Communicator it can send another message to the same recipient before receiving an acknowledgment for the previous one. This method is faster but in this case it is possible that the second message will be in fact delivered to recipient before the first one. When the message sequence is important (especially for control units) the “sending” is used. In this case a peripheral unit always waits for a message acknowledgment before sending another message to the same unit.

 Because of the nature of two-way communication, TWP Communicator can have only one name and this name mast be unique within one system (actually it is the system that rejects any attempt to give the same name to another unit). This makes impossible to send one single message to a group of Communicators. To support group sending a Group List (list of peripheral units) can be created in a Communicator and Communicator will automatically send appropriate number of messages when a message to a Group is sent.

One more new powerful instrument is a “Virtual Unit”. Virtual Unit is in fact a dynamic list of Unit Names and a set of rules how this list has to be maintained. Virtual Unit is programmed by administrator and stored in routers. A message can be sent to a Virtual Unit in the same way as to a real one. This message will be actually directed to a real Unit or to several Units in accordance to the rules for this Virtual Unit. For example: Virtual Unit “Administrator” keeps the name of a person who is currently responsible for the system administration. Another example is a “Customer Support” Virtual Unit. A message to the Customer Support will be actually sent to one of people in this list. The system keeps these Virtual Unit lists updated all the time. When a unit gets out of the covered area, the system suspends the unit name in all Virtual Unit lists automatically.

Installation and maintenance. Normally, an installation of a system that is as powerful as this one would need a lot of construction and wiring work. Maintenance would also require specially trained personnel. This new generation of wireless system does not require any special mounting or cabling. Indeed, the installation is a very simple procedure. All that has to be done is the installation of appropriate number of routers and beacons all over the covered area. Routers (as well as beacons) can be placed in any location that has electric power supply (lamp, fan, heater and so on). If there are no enough powered spots available, an accumulator or solar powered routers can be used. This system does not need any programming, dipswitch settings, and so on. As soon as a new device is in place, the system makes all the settings and initiation automatically. The easiest way to setup a new system is to select one of Typical Applications. Typical Application is in fact a set of system parameters that is the best for particular application.

In case of any malfunction in any part of this system the survived fraction of system generates a warning message to technical support personnel. The warning message displays the type of the broken part and its location. This information makes the maintenance of the system very simple. No extensive training is required, since a support person simply has to take a spare device from the stock and replace the broken one. The system supervises all the restoration processes and helps a technician to select a correct device and to install it properly.

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