ENHANCED POSITION LOCATION REPORTING SYSTEM
E NHANCED P OSITION L OCATION R EPORTING S YSTEM
5-10. The EPLRS consists of an RT, an operator interface device (the user readout), an antenna, and a power source (refer to Figure 5-1). The radio set provides transmission relay functions that are transparent to the user.
5-11. The EPLRS radio set has the following characteristics and capabilities— z Operates in the 420–450 MHz UHF frequency band.
z Provides secure, jam resistant digital communications and accurate position location capabilities.
z Uses TMDA, FH (512 times per second), and spread spectrum technology (eight frequencies between 420–450 MHz).
z Embedded COMSEC module, TRANSEC, and an adjustable power output provides secure communications with a LPI/D.
z BIT function that is activated at power turn on.
z Uses an omnidirectional dipole antenna capable of covering the 420–450 MHz frequency ranges.
z Provides wireless network extension functions that are transparent to the user. The maximum distance the EPLRS can cover is based on 3–10 km (1.8–6.2 miles) distance between each radio and the maximum number of relays in the link.
z Can handle up to 30 needlines. The maximum number of needlines available is dependent on the bps required for each needline.
5-12. There are four different configurations of the EPLRS— z AN/PSQ-6 manpack radio set.
z AN/VSQ-2 surface vehicle radio set. z ASQ-177C airborne radio set.
Figure 5-1. Enhanced position location reporting system
5-13. The RF network consists of many EPLRS radio sets connected to host computers. This provides secure host-to-host data communications for the host computers.
5-14. The radio set uses a wide band direct sequence spread spectrum waveform, TDMA, FH, and embedded error correction encoding. These capabilities provide for secure, high speed data communications networked between ground units and between ground units and aircraft. Most of the radio sets attributes are programmable and this programmability lets the planner set up the best possible anti-jam performance and data rate for the unique operational environment and mission.
5-15. EPLRS has automatic relay capabilities to support BLOS coverage. These capabilities are automatically and continually adapted to the changing operational environment faced by a mobile communications system.
5-16. The radio set also supports position location and identification capabilities. Position location allows users to determine precisely where the user is. It is similar to, but independent of, the GPS. Using position location data from the radio sets, some hosts may have the capability to determine where other radio sets are and can perform navigation functions.
Enhanced Position Location Reporting System Needlines Functions
5-17. Needlines are also known as a logical channel number or permanent virtual circuit. There can be many needlines running on a radio set at one time, supporting the hosts’ data communications needs. Needlines can be activated manually via the user readout or host, or automatically by the host. The radio set will automatically activate the needline if any data is received on the corresponding logical channel number. If the radio set is turned off or power is lost, active needlines will be automatically reactivated when the radio set is powered back on.
Types of Needlines
5-18. There are seven major types of needlines, each falling into the two major types of host-to-host services (broadcast and point-to-point)—
z Point-to-point needlines provide unequal data transfer capability for two endpoints’ hosts. Either endpoint can have all the data transfer capability, or it can be split between them in various ratios. Data is transferred at user data rates from 1,200 bps each way, up to 56,000 bps all one way. An example of how a point-to-point needline works would be the same as one person talking to another person on a telephone.
z Simplex (one-way) needlines provide a single host the capability to send data to many hosts. For simplex needlines, data is transferred at user data rates from 160–3,840 bps. An example of how a simplex needline works would be the same effect as using a bullhorn to talk to many
z CSMA needlines provide many hosts the capability to send data to each other. For CSMA needlines, data is transferred at user data rates from 150–487,760 bps (for the whole needline). The radio set ensures there are no other radio sets using the CSMA needline and then sends data from the host. When completed, another radio set will ensure no other radio sets are using the needline and then transmit, and so on. This protocol allows many endpoints’ hosts (multiple access) to use the same CSMA needline to send data to one or more endpoints’ hosts. An example of a CSMA needline would be like a group of people on a contention voice net, each speaking when they have something to say and no one else is speaking.
z Multisource group (MSG) needlines provide up to 16 hosts the capability to send data to many hosts. MSG needlines provide each source host guaranteed bandwidth without conflict, with user data rates from 37.5–485,760 bps. Data transferred from one source also goes to the other sources. If fewer sources are used, the sources can have more than 1/16th of the data transfer
capability. Each 1/16th is called a share. For example, a source endpoint can be assigned to have
4/16ths of the total MSG data transfer capability, with 12 other source endpoints each having
1/16th of the total MSG data transfer capability. If there are unused shares, a radio set whose
host load is larger than its assignment on the MSG needline will use these available shares. The more shares a radio set has, the more data transfer capability it has. The radio set also supports eight and four share MSG needlines that provide faster speed of service. An example of how an MSG needline works would be the same effect as up to 16 people with bullhorns talking, in a round robin fashion, to many people who cannot talk back. A MSG needline is similar to a CSMA needline, but each sender has a dedicated, guaranteed amount of time to talk (similar to many concurrent simplex needlines).
z Low data rate duplex (two-way) needlines provide radio-acknowledged, higher reliability, balanced data transfer between two hosts with data rates from 20–1920 bps each way. They provide equal data rates in both directions. This data transfer capability may be used by either or both endpoints. The endpoint radio sets will automatically ensure that the data is all delivered using radio set to radio set acknowledgement protocols. This needline type requires preplanning for the radio set to be able to use. An example of how a duplex needline works would be the same effect as talking to another person on a telephone.
z Dynamically allocated permanent virtual circuit (DAP) needlines are a special type of duplex needline. They have capabilities similar to those of duplex needlines (rates are 60–1920 bps), but DAP needlines are automatically set up and deleted on demand by the host, without any preplanning or NCS involvement. However, if the network resources are not available to support the data rate requested by the host, the needline rate is reduced to the highest rate available that the radio set can support.
z High data rate (HDR) duplex needlines have the same features as duplex needlines except that the data rates are higher, from 600–121,440 bps each way.
Enhanced Position Location Reporting System Communications Needlines Capabilities
5-19. An EPLRS radio set can support needlines as an endpoint, relay, or as both. A radio set can be a relay on some needlines, an endpoint on other needlines, and both an endpoint and a relay on other needlines, all at the same time. As an endpoint, a radio set can send and/or receive data to/from its host on a needline. A radio set that is only a relay (not an endpoint) cannot send or receive data to/from its host, and might not even have a host. For simplex, duplex, and DAP needlines, radio sets will automatically sign up as a relay if they have the resources available.
5-20. For point-to-point, CSMA, MSG, and HDR duplex needlines, a relay can only be endpoints on the needline, or they must be manually set up. When existing radio sets cannot support the EPLRS network relay needs, then dedicated relays are required.
5-21. There can be many host-to-host communications services running on a radio set at one time. There can be from one to thirty total needlines activated per radio set, depending upon the size of the needlines. If the maximum number is stored in the radio set, then another activated needline will cause the deletion of
the oldest stored needline. There can be a maximum of eight activated CSMA, HDR duplex, MSG, and point-to-point needlines, total, per radio set.
5-22. A needline can use any of four waveform modes, 0–3. The higher the waveform mode number, the higher data rate capability the needline has, but the lower the needlines anti-jam capabilities. (For more information on EPLRS and system components refer to TM 11-5825-283-10.)