DIGITAL RADIO SYSTEM SDH 7285-ODU SDH IDU

Transcription

1 DIGITAL RADIO SYSTEM SDH 7285-ODU SDH IDU 1

2 1 INTRODUCTION The SCREEN SERVICE Digital Radio System provides a cost-effective solution to high capacity data transmission requirements.operating from 4 to 38 GHz, it features a new compact IDU and ODU with enhanced features that include line interface, alarms and diagnostics, service channel and network management interfaces. Easy-to-install, the SCREEN SERVICE Digital Radio System provides user accessibility functions including Transmit Power, Receive Signal Level (RSL), and operating frequency. Additionally, the SCREEN SERVICE Digital Radio System features enhanced software allowing capacity / configuration upgrade, downloadable field upgrades and an optional embedded SNMP agent for advanced network management capabilities, making it the ideal solution for networks operated by mobile service providers, internet service providers (ISP), utilities, public telephone operators, local governments, TV networks and corporate users. The SCREEN SERVICE Digital Radios represent a new microwave architecture designed to address universal applications for both PDH and SDH platforms. This advanced technology platform is designed to provide the flexibility to customers for their current and future network needs. The SCREEN SERVICE Digital Radio Family is based upon a common platform to support a wide range of network interfaces and configurations. 2

3 1.1 Product Features Simple configuration reduces deployment time and lowers installation costs Compact and Lightweight Superior reliability -High MTBF Fully Calibrated Outdoor Unit 1U protected Indoor Unit It supports links for 32 x E1, 1 / 2 x 100BaseTX Ethernet, and 1 / 2 x STM-1 / OC-3. It is spectrum and data rate scalable, giving opportunity to service providers and companies to trade-off system gain with spectral efficiency and channel availability for optimal network connectivity. SCREEN SERVICE Digital Radio family enables network operators (mobile and private), access service providers and government to provide a portfolio of secure, scalable wireless applications for data, video, and voice over IP (VoIP). This family includes the following blocks: Indoor Unit (IDU) and Outdoor Unit (ODU). The Indoor Unit is designed to be frequency independent, and the Outdoor Unit is designed to be capacity independent. The IDU allows selection for multiple capacity options, radio frequency channels, modulation types and transmit output power levels to accommodate and adhere to worldwide standards and spectral efficiency requirements. The companion ODU can support frequency bands from 4 to 38 GHz. The IDU supports both 1+0 and 1+1 protection and Ring architectures, it is provided in a chassis arrangement 1U 19 inch standard rack. The modem and power supply functions are supported using easily replaceable plug-in modules. An additional feature of the IDU is provision for a second plug-in modem / IF module to provide repeater or transit network configurations (East/West). The SCREEN SERVICE Digital Radio System includes integrated Operations, Administration, Maintenance, and Provisioning (OAM&P) functionality and also Design features enabling simple commissioning for the radio network installation in the customer s premises. Another highlight of SCREEN SERVICE s Radio Products is the scalability and the capability to support a Ring architecture. This Ring or consecutive point radio architecture is self-healing in the event of an outage in the link and automatically re-routes data traffic, thereby ensuring the continuity of service to the end user. The overall architecture consists of a single 1U rack mount Indoor Unit (IDU) with a cable connecting to an Outdoor Unit (ODU) with an external antenna. 3

4 Figure 1 System Architecture In table 1 are listed key features that SCREEN SERVICE technology offers for broadband fixed wireless networks. Table 1. Key Benefits and Advantages of SCREEN SERVICE Digital Radios Benefits IDU Universal signal processing platform Advanced Single Chip Modem ASIC Integrated Forward Error Correction (FEC) Powerful adaptive equalizer Easy to install units Straightforward modular system enables fast deployment and activation. Carrier-class reliability. Advantages to Providers / Customers Enables easy network interface options and network capacity growth in the future. Cost effective solution; simplifying product logistics and overall product life cycle costs. The flexibility reduces capital and operating expenditures commonly associated with field installation, maintenance, training and spares. Frequency independent and Scalable. Software defined flexibility enables selective modulation for spectral efficiency and adherence to world-wide regulatory emissions guidelines. Fast return on investment. No monthly leased line fees. Complete support of payload capacity with additional voice orderwire 4

5 Aggregate capacity beyond basic network payload. Scalable and spectrally efficient system. Separate networks for radio overhead, management and user payload. Increases available bandwidth of network. Allows customer full use of revenue-generating payload channel. Lowers total cost of ownership. Comprehensive Link / Network Management Software A graphical user interface offers security, configuration, fault, and performance management via standard craft interfaces. Suite of SNMPcompatible network management tools that provide robust local and remote management capabilities. Simplifies management of radio network and minimizes resources as entire network can be centrally managed out of any location. Simplifies troubleshooting of single radios, links, or entire networks. Simplifies network upgrades with remote software upgrades. Allows for mass deployment Benefits Ring Architecture Supports a ring (consecutive point) configuration, thus creating a self-healing redundancy that is more reliable than traditional point-to-point networks. In the event of an outage, traffic is automatically rerouted via another part of the ring without service interruption. Ring / consecutive point networks can overcome lineofsight issues and reach more buildings than other traditional wireless networks. Networks can be expanded by adding more SCREEN SERVICE Digital Radios or more rings without interruption of service. A separate management channel allows for a dedicated maintenance ring with connections to each SCREEN SERVICE Digital Radio on the ring. Advantages to Providers/Customers Enables network scalability. Increases deployment scenarios for initial deployment as well as network expansion with reduced line-of-sight issues. Increases network reliability due to self-healing redundancy of the network. Minimizes total cost of ownership and maintenance of the network. Allows for mass deployment. Adaptive Power Control Enables dense deployment. Simplifies deployment Automatically adjusts transmit power in discrete and 5

6 increments in response to RF interference. 2 SYSTEM FEATURES network management. 2.1 Model Options Table 2 lists the SCREEN SERVICE digital radios according to model number and associated capabilities of throughput, data interface, and wayside channel. Table 2. SCREEN SERVICE Model Types and Options PRODUCT NAME FULL DUPLEX THROUGHPUT DATA INTERFACE WAYSIDE NP-LINKTM Scalable / / 8/12/16/32 E1 Base-TX / Mbps Ethernet* Scalable Fast Ethernet Mbps 100-BaseTX 4 x E1 NS-LINKTM Mbps 1 x STM-1: Scalable 100 Base-TX Optical / Electrical Ethernet* 1 x OC-3: Optical 4 x E1 * Scaled Ethernet values from 1-10 Mbps dependent on available bandwidth computed with payload data requirements and Voice Orderwire. Consult factory for scaled Ethernet with payload options. 6

7 2.2 Common Features Support for multiple configurations for both PDH and SDH 1+0, 1+1 protection Hot Standby East/West Repeater Selectable Spectral Efficiency of 0.8 to 6.25 bits/hz (including FEC and spectral shaping effects) QPSK, QAM Modulation Powerful Trellis Coded Modulation concatenated with Reed-Solomon Error Correction Built-in Adaptive Equalizer Support of Voice Orderwire Channels Peak output power: +20 dbm (will vary with ODU and frequency plan) Receive Sensitivity: -70 dbm (or lower, depending on data rate/modulation/fec/odu) Adaptive Power Control Built-in Network Management System (NMS) Consecutive Point ring architecture Built-in Bit Error Rate (BER) performance monitoring 2.3 NP-LINK TM Features The NP-LINK TM System is based on PDH (Plesiochronous Digital Hierarchy) Technology. PDH allows transmission of data streams that are nominally running at the same rate, but allowing some variation on the speed around a nominal rate. The basic data transfer rate is a data stream of Mbit/s (megabits/second). For speech transmission, this is broken down into 30 x 64 kbit/s (kilobits/second) channels plus 2 x 64 kbit/s channels used for signalling and synchronisation. Alternatively, the whole 2 Mbit/s may be used for non speech purposes, for example, data transmission. The exact data rate of the 2 Mbit/s data stream is controlled by a clock in the equipment generating the data. The exact rate is allowed to vary some percentage (+/-50 ppm) either side of an exact Mbit/s. This means 7

8 that different 2 Mbit/s data streams can be (probably are) running at slightly different rates to one another. In order to move multiple 2 Mbit/s data streams from one place to another, they are combined together, or "multiplexed" in groups of four. This is done by taking 1 bit from stream #1, followed by 1 bit from stream #2, then #3, then #4. The transmitting multiplexer also adds additional bits in order to allow the far end receiving multiplexer to decode which bits belong to which 2 meg data stream and so correctly reconstitute the original data streams. These additional bits are called "justification" or "stuffing" bits. Because each of the four 2 Mbit/s data streams is not necessarily running at the same rate, some compensation has to be made. The transmitting multiplexer combines the four data streams assuming that they are running at their maximum allowed rate. This means that occasionally, (unless the 2 Mbit/s really is running at the maximum rate) the multiplexer will look for the next bit but it will not have arrived. In this case, the multiplexer signals to the receiving multiplexer that a bit is "missing". This allows the receiving multiplexer to correctly reconstruct the original data for each of the four 2 Mbit/s data streams, and at the correct, different plesiochronous, rates. PDH Options Up to 16 x E1/T1 100BaseTX/Ethernet: Scalable Mbps DS-3/E-3/STS-1 8

9 Table 3. SCREEN SERVICE Model NP-LINK System Parameters Frequency 4/6 GHz 7/8 GHz 11 GHz 13 GHz Standards ETSI/FCC ETSI ETSI/FCC ETSI Operating Frequency ( GHz 4.60 to to to to ) 5.90 to 6.40 Channel BW 7 MHz Channel BW 14 MHz Channel BW 28 MHz QPSK 4E1 / 16 QAM 8E1 QPSK 16E1 / 16 QAM 32E1 128 QAM STM-1 Tx Power QPSK 27 dbm 24 dbm 16QAM 27 dbm 128QAM 27 dbm 20 dbm Rx 10-6 BER 4E1 / 8E1 91 / 86 dbm 91 / 86 dbm 16E1 / 32E1 85 / 78 dbm 85 / 78 dbm Frequency 15 GHz 18 GHz 23 GHz 31/38 GHz Standards ETSI ETSI/FCC ETSI/FCC ETSI/FCC Operating Frequency ( GHz ) to to to to to Channel BW 7 MHz Channel BW 14 MHz QPSK 4E1 / 16 QAM 8E1 Channel BW 28 MHz QPSK 16E1 / 16 QAM 32E1 Tx Power QPSK 24 dbm 22 dbm 21 dbm 16QAM 27 dbm 128QAM 27 dbm 18 dbm 17 dbm Rx 10-6 BER 4E1 / 8E1 91 / 86 dbm 90 / 85 dbm 16E1 / 32E1 85 / 78 dbm 84 / 77 dbm Frequency Stability % Background BER < Radio ETSI EN , EN , EN , EN Standards Compliance Power Supply ETSI EN Payload Interface Parameters EMC / Safety ETSI EN / IEC EN PDH Line Rate 1 to 32 x E1 / T1 Interfaces 120 balanced or 75 unbalanced Standards Compliance ITU-T G.703, G.783 9

10 Line Rate Full Duplex, scalable up to 100 Mbps Ethernet Interfaces 100 Base-Tx Standards Compliance IEEE Configuration Mechanical / Environmental Dimensions Weight Operating Temperature Altitude Humidity Power Input Power Consumption Cooling Coaxial Interfaces IDU-ODU Cable Antenna Interface IDU: 19" standard rack (1U), 445 x x 44.5mm ODU: 240mm x 240mm x 70mm IDU: 4 Kg; ODU: 6.0 Kg IDU: -5 to +45 C; ODU: -33 to +55 C Up to 4500 meters IDU: 95% condensing; ODU: 100% all-weather -48V DC (-36V to -60V DC) IDU: < 25 watts; ODU: <25 watts Natural convection IDU TNC female, ODU N-type female Belden 9913/RG-8, up to 300m Standards Compliance ETSI ETS Network Management Coaxial N-type connector (6-11 GHz); proprietary direct mount (13GHz and above) Support Local Access Control Channel SNMP, Fully featured MIB, WEB based GUI, Embedded HTML server, CLI Ethernet 10/100 Base-T / RJ-45 In band 10

11 2.4 NS-LINK TM Features The synchronous optical network, commonly known as SONET, is a standard for communicating digital information using lasers or light emitting diodes (LEDs) over optical fiber. It was developed for transporting large amounts of telephone and data traffic and to allow for interoperability between equipment from different vendors. The more recent synchronous digital hierarchy (SDH) standard is built on experience in the development of SONET. It is documented in standard G.707 and its extension G.708. Both SDH and SONET are widely used today; SONET in the U.S. and Canada, SDH in the rest of the world. SDH is growing in popularity and is currently the main concern with SONET now being considered as the variation. SDH uses exact rates that are used to transport the data are tightly synchronized across the entire network, made possible by atomic clocks. This synchronization system allows entire intercountry networks to operate synchronously, greatly reducing the amount of buffering required between each element in the network. Both SONET and SDH can be used to encapsulate earlier digital transmission standards or used directly to support either ATM or so-called Packet over SONET networking. The basic unit of transmission for SONET is a signal that operates at Mbit/s, designated STS-1 (Synchronous Transport Signal one). SDH's basic unit, the STM-1 (Synchronous Transport Module-level 1), operates at three times that rate, Mbit/s. The two major components of the STS-1 frame are the transport overhead and the synchronous payload envelope (SPE). The transport overhead (27 bytes) comprises the section overhead and line overhead. These bytes are used for signalling and measuring transmission error rates. The SPE is comprised of two components: the payload overhead (9 bytes, used for end to end signalling and error measurement) and the payload of 774 bytes. The STS-1 payload is designed to carry a full DS-3 frame. When the DS-3 enters a SONET network, path overhead is added, and that SONET network element is said to be path terminating. Where multiple DS-3 paths are multiplexed, the SONET NE is said to be line terminating. Note that wherever the line or path is terminated, the section is terminated also. SONET Regenerators (see below) terminate the Section but not the path or line. The entire STS-1 frame is 810 bytes. The STS-1 frame is transmitted in exactly 125 microseconds on a fiberoptic circuit designated OC-1 (optical carrier one). In practice, the terms STS-1 and OC-1 are sometimes used interchangeably, though the OC-N format refers to the signal in its optical form. It is therefore incorrect to say that an OC-3 contains 3 OC-1s: an OC-3 can be said to contain 3 STS-1s. Three OC-1 (STS-1) signals are multiplexed by time-division multiplexing to form the next level of the SONET hierarchy, the OC-3 (STS-3), running at Mbit/s. The multiplexing is performed by interleaving the bytes of the three STS-1 frames to form the STS-3 frame, containing 2430 bytes and transmitted in 125 microseconds. SDH Options 11

12 1-2 x SDH STM-1/OC-3 SONET TM System Parameters Table 4. SCREEN SERVICE Model NS-LINK Frequency 4/6 GHz 7/8 GHz 11 GHz 13 GHz Standards ETSI/FCC ETSI ETSI/FCC ETSI Operating Frequency ( GHz 4.60 to to to to ) 5.90 to 7.10 Channel BW 28 MHz Channel BW 56 MHz 128 QAM STM-1 32 QAM STM-1 / 128 QAM 2*STM-1 Tx Power 27 dbm 19 dbm Rx 10-6 BER 28 MHz, STM-1 68 dbm 68 dbm 56 MHz, STM-1 / 2xSTM-1 70 / 65 dbm 70 / 65 dbm Frequency 15 GHz 18 GHz 23 GHz 31/38 GHz Standards ETSI ETSI/FCC ETSI/FCC ETSI/FCC Operating Frequency ( GHz ) to to to to to Channel BW 7 MHz Channel BW 14 MHz 16 QAM 32E1 / 128 QAM STM-1 Channel BW 28 MHz 32 QAM STM-1 / 128 QAM 2*STM-1 Tx Power 27 dbm 17 dbm 15 dbm Rx 10-6 BER 4E1 / 8E1-68 dbm 66 dbm 16E1 / 32E1 70 / 65 dbm 68 / 63 dbm Frequency Stability % Background BER < Radio ETSI EN , EN , EN , EN Standards Compliance Power Supply ETSI EN Payload Interface Parameters SDH Line Rate Interfaces Standards Compliance EMC / Safety ETSI EN / IEC EN or 2 STM-1/OC Mbps Optical Type SC single mode 1310nm, Electrical BNC Telcordia Line Rate Full Duplex, scalable up to 100 Mbps Ethernet Interfaces 100 Base-Tx Standards Compliance IEEE

13 Configuration Mechanical / Environmental Dimensions Weight Operating Temperature Altitude Humidity Power Input Power Consumption Cooling Coaxial Interfaces IDU-ODU Cable Antenna Interface IDU: 19" standard rack (1U), 445 x x 44.5mm ODU: 240mm x 240mm x 70mm IDU: 4 Kg; ODU: 6.0 Kg IDU: -5 to +45 C; ODU: -33 to +55 C Up to 4500 meters IDU: 95% condensing; ODU: 100% all-weather -48V DC (-36V to -60V DC) IDU: < 25 watts; ODU: <25 watts Natural convection IDU TNC female, ODU N-type female Belden 9913/RG-8, up to 300m Standards Compliance ETSI ETS Coaxial N-type connector (6-11 GHz); proprietary direct mount (13GHz and above) Network Management Support Local Access Control Channel SNMP, Fully featured MIB, WEB based GUI, Embedded HTML server, CLI Ethernet 10/100 Base-T / RJ-45 In band 13

14 3 PHYSICAL DESCRIPTION The following section details the physical features of the SCREEN SERVICE digital radios Model Options Front and rear panel configurations LED descriptions 3.1 Front Panel Indicators All models of the SCREEN SERVICE Digital Radios support a variety of front panel configurations that are dependent on the network interface and capacity configurations. Figure 2 provides an example of the PDH 8/12/16 E1/T1 1+0 configuration and the associated LEDs displayed on the IDU front panel. TM 14

15 Figure 2. LEDs: IDU Front Panel Configuration for NP-LINK, 1+0 Configuration 3.2 Front Panel Connections Please refer to the Figure 3 for an example of a SCREEN SERVICE IDU front panel followed by a descriptive text of the connections. Figure 3. NS-LINK, 1+1 Protection: IDU Front Panel Connections TM The recommended maximum length for all cables to terminal equipment is a maximum of 3 meters. The exception to this recommendation is the length of the ODU/IDU Interconnect cable, which connects the Outdoor Unit to the Indoor Unit. 15

16 4 SYSTEM DESCRIPTION The overall digital radio architecture consists of a single 1RU rack mount Indoor Unit (IDU) with a cable connecting to the Outdoor Unit (ODU) with an external antenna. Figure 4. Indoor Unit Block Diagram Figure 4 shows the IDU and interfaces from a functional point of view. The functional partitions for the I/O, 16

17 Modem/IF, and power supply modules are shown. The IDU comes with the standard I/O capability which can be upgraded. In addition, the Modem/IF function is modular. This allows the addition of a second Modem to support protection or ring architectures. The power supply is similarly modular. The major functions of the IDU can be summarized as follows: I/O Processing The IDU comes with a standard I/O capability that includes support for up to 16xT1/E1 and 2x100Base-TX user payloads, 2x100Base-TX for SNMP, and voice orderwire. In addition, option cards for DS-3/E3/STS-1, 1-2 x STM-1/OC-3, and 4xDS-3/E3/STS-1 may be added. The IDU architecture is flexible and allows for the addition of other I/O types in the future. Switch/Framing The IDU includes an Ethernet Switch and a proprietary Framer that are designed to support 1+1 protection switching, ring architecture routing, and overall network control functions. Network Processor The IDU includes a Network Processor which performs SNMP and Network Management functions. Modem/IF The IDU Modem performs forward-error-correction (FEC)encoding, PSK/QAM modulation and demodulation, equalization, and FEC decoding functions. The IF chain provides a 350 MHz carrier and receives 140 or 60 MHz carriers. The multiplexer function is built into an appliqué that resides in the Modem/IF Module. Two modems can be used for 1+1 protection or ring architectures. a. Power Supply The IDU power supply accepts -48 Vdc and supplies the IDU and ODU with power. A second redundant power supply may be added as an optional module. b. For the OC-3 configuration, a user rate clock is recovered from clock recovery NCO and provided to the OC-3/STM-1 I/O card. The Modem Processor and its associated RAM, ROM, and peripherals control the digital and analog Modem operation. It also provides configuration and control for both the IF and I/O cards. The IDU interfaces with the ODU to receive and provide modulated transmit and receive waveforms. The 256-QAM Modem performs the modulation and demodulation of the payload/wayside/snmp data and forward error correction using advanced modulation and coding techniques. Using all-digital processing, the 256- QAM Modem uses robust modulation and forward error correction coding to minimize the number of bit errors and optimize the radio and network performance. The 256-QAM Modem also scrambles, descrambles and interleaves/deinterleaves the data stream in accordance with Intelsat standards to ensure modulation efficiency and resilience to sustained burst errors. The modulation will vary by application, data rate, and frequency spectrum. The highest order modulation mode supported is 256 Quadrature Amplitude Modulation (QAM). Table 2-3 summarizes the TCM/convolutional code rates for each modulation type supported by the Digital Radio. 17

18 Table 4. SCREEN SERVICE Digital Radio TCM/Convolutional Code Rates Modulation CC/TCM Code Rate Reed Solomon Code Rate BPSK 1 / 2 3 / 4 (1) (1) QPSK 1 / 2 3 / 4 (1) (1) 16 QAM TCM 3 / 4 7 / 8 (1) (1) 32 QAM TCM 4 / 5 9 / 10 (1) (1) 64 QAM TCM 5 / 6 11 / 12 (1) (1) 128QAM TCM 6 / 7 13 / 14 (1) (1) 256 QAM TCM 7 / 8 15 / 16 (1) (1) Notes: (1) Codeword byte length, N: ; Message byte length, K: ; check byte length, N-K: 2-20 The RS encoding shall be programmable over the following ranges Codeword Byte Length 200 to 255 in steps of 1 Message Byte Length 184 to 253 in steps of 1 18

19 Check Bytes 2 to 20 in steps of 2 Correctable Bytes =Check Bytes/2 The IDU also provides the physical interface for the user payload and network management. In transmit mode, the Framer merges user payload (OC-3 or Fast Ethernet) with radio overhead-encapsulated network management data. This combined data stream is transmitted without any loss of user bandwidth. In the receive mode, the Framer separates the combined data stream received from the 256-QAM Modem. The IDU supports Scalable Ethernet data rates, such as 25 or 50 Mbps via the 100BaseT data interface port. The MAN_DRS_NL.DOC IDU provides network management data on 10 Mbps ports accessible via the 10/100BaseTX port. The Central Processor Unit (CPU) provides the embedded control and network element functionality of the OAM&P. The CPU also communicates with other functions within the IDU for configuration, control, and status monitoring. The CPU passes appropriate status information to the IDU front panel display. The power supply converts 48 Vdc to the DC voltage levels required by each component in the system. 5 CONSECUTIVE POINT ARCHITECTURE The consecutive point network architecture is based upon the proven SONET/SDH ring. Telecommunications service providers traditionally use the SONET/SDH ring architecture to implement their access networks. A typical SONET/SDH network consists of the service provider s Point of Presence (POP) site and several customer sites with fiber optic cables connecting these sites in a ring configuration (see Figure 5). This architecture lets providers deliver high bandwidth with high availability to their customers. 19

20 Figure 5. Ring Configuration SONET/SDH rings are inherently self-healing. Each ring has both an active path and a standby path. Network traffic normally uses the active path. Should one section of the ring fail, the network will switch to the standby path. Switchover occurs in seconds. There may be a brief delay in service, but no loss of payload, thus maintaining high levels of network availability. The consecutive point architecture implemented in the NS-LINKis based on a point-to-point-to-point topology that mimics fiber rings, with broadband wireless links replacing in-ground fiber cable. A typical consecutive point network consists of a POP and several customer sites connected using SCREEN SERVICE units. These units are typically in a building in an east/west configuration. Using east/west configurations, each unit installed at a customer site is logically connected to two other units via an over-the-air radio frequency (RF) link to a unit at an adjacent site. Each consecutive point network typically starts and ends at a POP. A pattern of wireless links and in-building connections is repeated at each site until all buildings in the network are connected in a ring as shown in Figure 6. TM MAN_DRS_NL.DOC 20

21 Figure 6. Consecutive Point Network 6 POWER MANAGEMENT RF power management is a radio design feature that controls the power level (typically expressed in dbm) of the RF signal received from a transmitter by a receiver. The traditional goal of power management is to ensure that the RF signal at a receiver is strong enough to maintain the radio link under changing weather and link conditions. Traditional power management techniques such as Constant Transmit Power Control (CTPC) and Automatic Transmit Power Control (ATPC) transmit at a high power level to overcome the effects of fading and interference. However, these techniques continue to operate at a higher power level than needed to maintain the link in clear weather. Because transmit power remains high when the weather clears, the level of system interference increases. 21

22 Radios operating at high transmit power will interfere with other radios, even if the interfering source is miles away from the victim. High interference levels can degrade signal quality to the point that wireless radio links become unreliable and network availability suffers. The traditional solution to system interference is to increase the distance between radios. However, the resulting sparse deployment model is inappropriate for metropolitan areas. In response to the need for a high-density deployment model the SCREEN SERVICE Digital Radio System use a unique power control technique called AdTPC. This power management enables SCREEN SERVICE units to transmit at the minimum power level necessary to maintain a link regardless of the prevailing weather and interference conditions. It is designed and manufactured to not exceed the +30 dbm maximum power allowed. The purpose of power management is to minimize transmit power level when lower power levels are sufficient. AdTPC also extends the concept of power management by controlling not only the power (dbm) of the RF signal, but its quality (signal-to-noise ratio) as well. In contrast to ATPC, the AdTPC technique dynamically adjusts the output power based on both the actual - strength and quality of the signal. Networked SCREEN SERVICE units constantly monitor receive power and maintain 10 BER performance under varying interference and climate conditions. Each SCREEN SERVICE unit can detect when there is a degradation in the received signal level of quality and adjust the transmit power level of the far-end SCREEN SERVICE unit to correct for it. AdTPC provides maximum power in periods of heavy interference and fading and minimum power when conditions are clear. Minimal transmit power reduces potential for co-channel and adjacent channel interference with other RF devices in the service area, thereby ensuring maximum frequency re-use. The resulting benefit is that operators are able to deploy more SCREEN SERVICE units in a smaller area. 7 NETWORK MANAGEMENT All of the SCREEN SERVICE Digital Radio parameters are accessible in three ways: Using a standard web-browser via HTTP top access the built in web server. Via SNMP using the fully featured MIB, allowing for automation of data collection and network management. Via a command line client accessible from a terminal client connected to the serial port, or telnet over the NMS Ethernet. 22

23 Control of the SCREEN SERVICE digital radio family is supported as follows: PC-based Graphical User Interface.. This GUI applies for all SCREEN SERVICE product delivered and fielded from June Network Management options. This NMS applies for all SCREEN SERVICE product delivered and fielded from June