Residential Microwave Systems

1. Residential Microwave Systems Jason Blake Nate Slabaugh

2. Introduction Residential microwave systems Use licensed frequencies in 2.5 GHz (MMDS) and 20 GHZ (LMDS) band Fixed broadband wireless access (BWA) Alternative to landline access such as cable and dsl

3. Background MMDS Multichannel Multipoint Distribution Service 2.5 to 2.7 GHz Originally consisted of 33 analog channels Range can reach 35 miles

4. Background MMDS - spectrum

5. Background MMDS Wireless cable ITFS - instructional television fixed service Not popular because of competition from cable, broadcast, and satellite Because of this FCC amended rules for MMDS spectrum

6. Background LMDS Local Multipoint Distribution System 20 to 40 GHZ range Range limited to 4 or 5 miles Affected by adverse weather

7. Background LMDS Spectrum was allocated specifically for fixed wireless access Allows for huge data rates Has greater line of sight (LOS) requirements than MMDS

8. Modulation Many modulation schemes can be used TDMA/FDD FDMA/FDD TDMA/TDD CDMA/FDD

9. Modulation OFDM Orthogonal Frequency Division Multiplex Uses orthogonal properties of transmission pulses to address some of the issues with 1st generation systems Can be used with TDMA, FDMA, CDMA

10. MMDS Architecture Super-Cell Multi-Hub

11. Super-Cell Omni-directional Sectorized Increases Capacity Up to 12 sectors Reuse frequencies

12. Super-Cell Requirements Highest Point Surrounding area needs to be relatively flat Sprint has transmitter on Sear�s Tower in Chicago and South Mountain in PhoenixSprint has transmitter on Sear�s Tower in Chicago and South Mountain in Phoenix

13. Multi-Hub Multiple, smaller towers Can be sectorized Frequency reuse More tolerant of hilly terrain Capacity can be increased by adding more hubs

14. MMDS Tower Configuration Receiving Antenna Waveguide Low-Noise Amplifier Downconverter Headend equipment Gateway router Internet If the tower is sectorized, there are usually several receive antennas in order to have better reception and to increase the capacity of the return spectrum. When receiving, a waveguide is used to send the RF signals to a downconverter. Sometimes, a low-noise amplifier is used to boost the signal before it gets to the downconverter. From the downconverter, an intermediate frequency (IF) signal is sent to the headend equipment that demodulates the signal. From there a gateway router is used to connect with the Internet.If the tower is sectorized, there are usually several receive antennas in order to have better reception and to increase the capacity of the return spectrum. When receiving, a waveguide is used to send the RF signals to a downconverter. Sometimes, a low-noise amplifier is used to boost the signal before it gets to the downconverter. From the downconverter, an intermediate frequency (IF) signal is sent to the headend equipment that demodulates the signal. From there a gateway router is used to connect with the Internet.

15. MMDS Tower Configuration Transmitting Internet Gateway router Headend equipment Transmitter Waveguide Antenna When transmitting, the information taken from the gateway router is modulated by the headend equipment, which is then passed to the transmitter. From there, a waveguide takes the signal to the antenna. Usually, an Ethernet switch is used to connect the most of the components togetherWhen transmitting, the information taken from the gateway router is modulated by the headend equipment, which is then passed to the transmitter. From there, a waveguide takes the signal to the antenna. Usually, an Ethernet switch is used to connect the most of the components together

16. MMDS Customer Side Small transciever/antenna Wireless broadband router Customer�s computer or LAN On the customer side, a small (around 13 x 13 inch) digital transceiver, which is also the antenna, is placed on the customer�s roof or mast, if needed, with a line of sight to the transmitter. The transceiver converts the RF signal to IF and then passes it to the wireless broadband router (WBR), or cable modem, via coaxial cabling. From there it is given to either the customer�s PC using an Ethernet Card or the customer�s LANOn the customer side, a small (around 13 x 13 inch) digital transceiver, which is also the antenna, is placed on the customer�s roof or mast, if needed, with a line of sight to the transmitter. The transceiver converts the RF signal to IF and then passes it to the wireless broadband router (WBR), or cable modem, via coaxial cabling. From there it is given to either the customer�s PC using an Ethernet Card or the customer�s LAN

17. Example from Hybrid Your computer (1) sends a request for data or a Web page to the MMDS modem. �The MMDS modem sends the data request to the receiver/ transmitter (2) on the user's roof. �The receiver/ transmitter sends the data in a 2.1 GHz signal at speeds up to 10 megabits per second to the receive/ transmit tower (3). The tower relays the data request through the network to the Internet Service Provider (ISP) facility (4). �The ISP receives the request and retrieves data either from its servers or from the Internet (5) over its high-speed backbone connection. �The ISP than returns the data via the network to the receive/ transmit tower. The transmit site sends the data in a 2.5 GHz signal at speeds up to 10 megabits per second to the receiver on the user's roof. �The roof-mounted receiver relays information to the MMDS modem. The modem passes the information to a stand-alone PC or Macintosh computer or to multiple users in a LAN all in seconds. Your computer (1) sends a request for data or a Web page to the MMDS modem. �The MMDS modem sends the data request to the receiver/ transmitter (2) on the user's roof. �The receiver/ transmitter sends the data in a 2.1 GHz signal at speeds up to 10 megabits per second to the receive/ transmit tower (3). The tower relays the data request through the network to the Internet Service Provider (ISP) facility (4). �The ISP receives the request and retrieves data either from its servers or from the Internet (5) over its high-speed backbone connection. �The ISP than returns the data via the network to the receive/ transmit tower. The transmit site sends the data in a 2.5 GHz signal at speeds up to 10 megabits per second to the receiver on the user's roof. �The roof-mounted receiver relays information to the MMDS modem. The modem passes the information to a stand-alone PC or Macintosh computer or to multiple users in a LAN all in seconds.

18. Dynamically Assigned Bandwidth MMDS targeted to small business and residential customers Low average use Require high bandwidth while in use Because the technology is targeted to small businesses and residential customers who typically have low average use but need high bandwidth when in use, the MMDS system bandwidth is dynamically assigned. Theoretically, this allows each customer to share a larger bandwidth pool. The capacity of the system is determined by how many channels are available, the number of cells deployed, frequency reuse, sector pattern, and customer demand.Because the technology is targeted to small businesses and residential customers who typically have low average use but need high bandwidth when in use, the MMDS system bandwidth is dynamically assigned. Theoretically, this allows each customer to share a larger bandwidth pool. The capacity of the system is determined by how many channels are available, the number of cells deployed, frequency reuse, sector pattern, and customer demand.

19. Bandwidth Sprint claims 10Mbps Hybrid 10 to 30 Mbps downstream 32Kbps to 10Mbps upstream

20. LMDS

21. LMDS Smaller coverage area Limited because the wavelength is smaller which allows for interference by rain, snow, and fog 2 to 5 miles Cheaper Good for cities More bandwidth 1.5 Gbps LMDS is very similar to MMDS, except that for each base station the coverage is much smaller. Since the wavelength of the LMDS signal is smaller than that of MMDS, rain, snow, and fog can cause interference, which limits the coverage area to around 2 to 5 miles. However, it is cheaper to set up a cell. In an urban setting this can be an advantage over MMDS. Because MMDS cells are more expensive it is very inefficient to set up a MMDS system in a city since having large buildings blocking the signals negates the advantage of MMDS having a larger range.LMDS is very similar to MMDS, except that for each base station the coverage is much smaller. Since the wavelength of the LMDS signal is smaller than that of MMDS, rain, snow, and fog can cause interference, which limits the coverage area to around 2 to 5 miles. However, it is cheaper to set up a cell. In an urban setting this can be an advantage over MMDS. Because MMDS cells are more expensive it is very inefficient to set up a MMDS system in a city since having large buildings blocking the signals negates the advantage of MMDS having a larger range.

22. MMDS Use Sprint Phoenix Tuscan Chicago MCI WorldCom Boston Dallas Smaller markets in Mississippi, Lousiana, and Tennessee While Sprint and WorldCom are both concentrating on MMDS, they are targeting different groups. WorldCom�s main targets are small businesses, and Sprint appears to be going after the residential market.While Sprint and WorldCom are both concentrating on MMDS, they are targeting different groups. WorldCom�s main targets are small businesses, and Sprint appears to be going after the residential market.

23. MMDS Use Map of WorldCom licenses. BTA - basic trading area PSA - protected service areBTA - basic trading area PSA - protected service are

24. MMDS Equipment Sprint uses: Cisco Systems Hybrid Networks ADC Telecommunications WorldCom Hybrid ADC Nortel Net-works

25. LMDS Nextlink Communications Inc. CenturyTel

26. Standards Wireless DSL Consortium Formed by communications and semiconductor companies Define and Implement and open MMDS standard Guidelines for testing and verification of wireless broadband testing The Wireless DSL Consortium was formed by several companies to form an open standard. The companies involved fear that different technology choices available it will slow growth in the market like the situations with Digital Subscriber Line and cable markets. Currently, the service providers that want to offer broadband wireless must choose between a large amount of different technologies which slows down the speed of deployment. The companies hope that by reaching a common standard, they can make the MMDS market bigger. The consortium also hopes to provide guidelines for testing and verification standards for wireless broadband equipment. Gigabit Wireless, a company involved with the Consortium, is working on �smart antennas� in conjuction with multi-carrier technology which they hope will increase capacity and coverage and solve many �line-of-sight� problems. Sprint and WorldCom have joined with Nucentrix Internet Services to come up with a plan to avoid interference between different MMDS license areas.The Wireless DSL Consortium was formed by several companies to form an open standard. The companies involved fear that different technology choices available it will slow growth in the market like the situations with Digital Subscriber Line and cable markets. Currently, the service providers that want to offer broadband wireless must choose between a large amount of different technologies which slows down the speed of deployment. The companies hope that by reaching a common standard, they can make the MMDS market bigger. The consortium also hopes to provide guidelines for testing and verification standards for wireless broadband equipment. Gigabit Wireless, a company involved with the Consortium, is working on �smart antennas� in conjuction with multi-carrier technology which they hope will increase capacity and coverage and solve many �line-of-sight� problems. Sprint and WorldCom have joined with Nucentrix Internet Services to come up with a plan to avoid interference between different MMDS license areas.

27. The Future Standards IEEE 802.16 (wireless man) Based on 802.11a (wireless lans) Standard is being written as we speak When finalized will lead to growth in industry for wireless man

28. The Future Price Currently customer premise equipment (CPE) very expensive 2nd generation promises to be more affordable

29. The Future OFDM - revisited 2nd generation will implement Promises to alleviate LOS issues Fights multipath interference

30. The Future OFDM - how it works FDM uses guard bands

31. The Future OFDM - how it works No guard bands Spectral efficiency

32. The Future OFDM - how it works Uses parallel streams of low bit rate data instead of serial high bit rate data To ensure sub channels are orthogonal symbols are constructed in frequency domain IFFT converts frequency domain signal to time domain signal

33. The Future OFDM - how it works To reduce intersymbol interference caused by multipath, a guard band is inserted in the time domain

34. The Future VOFDM Vector Orthogonal Frequency Division Multiplex Adds spatial diversity This means it uses a second antennae

35. The Future VOFDM - example

36. The Future VOFDM-example Two antennae combine to mitigate effects of multipath

37. The Future VOFDM - performance

38. The Future VOFDM VOFDM actually takes advantage of multipath interference, improving signal quality even when not operating in LOS of tranciever

39. Questions?????