1.Cable access technolog&wireless access 2.Micro wave antennas,waveguides, and towers&Microwave application issues
Access Technologies and Microwave Radio SystemsO.Bat-Erdene(J.TC08D027) G.Uranchimeg(J.TC08D718)A.Ulziisuren(J.TC08D702) Access Technologies
Small business and residences use one of thetechnologies described in this chapter: DSL , cable, or wireless.
DSL-Digital Subscriber Line
DSL operates over the ILECs copper wire local loop. Although the loop is not ideal for broadband communications, it is widely available, inexpensive, and does the job effectively. ILEC Incumbent Local Exchange Carrier
DSL standardsHDSL High Bit-Rate Digital Subscriber LineADSL Asymmetric Digital Subscriber LineSDSL Single-Pair Digital Subscriber LineVDSL Very High Bit Rate Digital Subscriber LineG.Lite Splitter less Digital Subscriber Line
Asymmetric Digital Subscriber Line (ADSL)
ADSL is the most common type and is most attractive for casual users.
Rate (downstream) 1.5MbpsRate (upstream) 64-640Kbps
Very High Bit-Rate Digital Subscriber Line (VDSL)VDSL was developed to support video or high-speed data.
High rate 52Mbps , range -1000ft(330m)
Drop rate 13Mbps , range -4500ft(1500m)
High-Speed Digital Subscriber Line (HDSL)
ILECs use HDSL to provide T1/E1 service over two twisted pair wires up to 12,000 ft (4000 m) long.
This service is not sold to subscribers as DSL service, but as T1/E1 point-to-point service.
Single-Pair Digital Subscriber Line (SDSL)
SDSL, also known as symmetric DSL, provides T1/E1 service on a single cable pair and derives a POTS line under the data signal. It transmits and receives in the same band of frequencies using an echo-canceling protocol.
Cable Access Technology
Cable operators inject information and entertainment channels at the head end.Standard TV channel:6MHz wideQAM modulation1channel= 27Mbps of downstream data
The service provider decides how many subscribers will share the bandwidth. There are 2 streams:
Data Over Cable System Interface Specification(DOCSIS)DOCSIS is an international Telecommunication Standard. Consortium of equipment manufacturers developed DOCSIS as a standard method of providing Internet access. In Europe=>Euro-DOCSIS(USAs version) Over a 6 MHz Radio Frequency channel
DOCSIS is designed for cable but it can also be used in Wireless MultipointMultichannel Distribution Service(MMDS)
Link security layer consists of 3 security protocols:Baseline Privacy Interface(BPI) =>encrypt data traffic between the users modem Security System Interface(SSI)Removable Security Module Interface(RSMI)
DOCSIS compared to OSITCP-Transmission Control ProtocolUDP-User Diagram ProtocolIEEE 802.2 protocol of LLC(Logical Link Control) standard TDMA-Time Division Multiple AccessMPE-2 Motion Picture Experts Group 2 QPSK- Quadrature Phase Shift Keying
Wireless AccessWireless is the broadband access method to provide many users as Internet.Service: - Licensed(Satellite, Cellular) -Unlicensed (802.11)
Wireless has a cable with medium is shared.Downstream UpstreamFDMA(Frequency Division Multiple Access)TDMA(Time Division Multiple Access)CDMA (Code Division Multiple Access)Why wireless access?
Wi-Fi 802.11 and WiMAX 802.16Wi-Fi 802.11(Wireless Fidelity)- standard for unlicensed frequenciesWi-Fi frequency Ranges:2.4GHz band(older)2.4-2.4835GHz11unlicensed communications channels5GHz band(newer)5.1GHz; 5.3GhH; 5.4GHz; 5.8GHz24 unlicensed bands
Wi-Fi benefit: Wide range It covers airport, coffee shops, some street corners
WiMAX 802.16 (Worldwide Interoperability for Microwave Access)WiMAX range is around 16km.WiMAX benefits:High securityLow costOpen standardsWide coverage
WiMAX Applications:Gaming with many playersVideo ConferencingStreaming MediaWeb browsing and Instant MessageMedia content Downloads
MMDS(Multipoint Multifrequency Distribution Service)
MMDS was originally intended as a wireless replacement for cable television with 200 MHz of spectrum allocated between 2.5 and 2.7 GHz.
CDPD (Cellular Digital Packet Data)
CDPD is a packet overlay on cellular sites.
3G: Third Generation Cellular
Third generation (3G) cellular is intended to support Internet access from a cell phone or equivalent.
Regulatory Issues:In the United States, Congress and the FCC have a major role to play in broadband development and the outcome is difficult to predict.
Choice of Medium:Cable access is available in localities in which the cable operator has upgraded the facility to two-way and provides access service over the cable.
Voice and Video ServiceInternet access is asymmetric in nature, so the limited upstream bandwidth of cable, wireless, and DSL are appropriate.
Micro radio system is included in access technology. Microwave Radio SystemsMicrowave Technology
Radio Signal PropagationWhen designing microwave systems, engineers take into account the following conditions that affect signals:
Free-space lossAtmospheric attenuationReflectionDiffractionRain attenuation
Microwave systemsParabolic Horn Antennas The general principles of microwave radio are the same as those of lower frequency radio.
A second cause of fading is heavy rain, which absorbs part of the transmitted power. The effect is most detrimental at frequencies higher than about 10 GHz. Diversity, as described in a later section, alleviates the two primary causes of microwave path disruption, which are fading and equipment failures.
Microwave RepeatersPoint-to-point microwave routes are established by connecting a series of independent radio paths with repeater stations. Line of sight is required between the transmitting and receiving antennas for all microwave systems except MIMO and those that use forward scatter techniques to transmit beyond the horizon.
Multipath Fading and Interferences
Cross polarization- 20to 30dB
Microwave antennasMicrowave antennas features:
Parabolic dishesHornsDiametersLess than 1m for short distance30m for Earth Station Satellite SystemsConnected by coaxial cable
Some troubles(because of our environment)When microwave signal radiates into free spaces, it is attenuated by losses. Losses are:Temperature inversionsRainFogSnowLightning so on.
Thank you for your attention!