Line-of-Sight IP Networks

Johnathan PoarchSenior Information Tech Specialist

Line-of-Sight (LoS) History

• Early LoS systems developed by US military in the 1940s.

• Extensive TeleCom use in 1950s and 1960s for LD and TV (AT&T Long Lines System)

• Modern use by TV relay and backbone carriers for cellular systems

Use of LoS in IT• Intra-campus IP/VoIP/CCTV (fiber replacement)• Site-to-Site connectivity• Temporary or backup connectivity to

WAN/Internet

Typical LoS Topologies

• Point-to-Point• Point-to-Multipoint• Mesh

LoS Planning Considerations

• Affected greatly by environmental constraints, including rain fade

• Very limited penetration capabilities through obstacles such as hills, buildings and trees

• Sensitive to high pollen count• Signals can be degraded during Solar events

Common Types of LoS Systems

• Microwave• Directional (long range) WiFi• Laser • Leased systems

Microwave LoS

• Most common for short range data “back hauls”

• Licensed Bands – Higher frequency and power• Unlicensed Bands – Lower initial cost; plug

and play (solutions start under $5,000)

Directional WiFI

• High signal noise in 2.4GHz band• Commercial 802.11 radios can be used with

directional antennas • Amplifiers can also be used to extend range

Laser LoS

• Secure data transmission• Up to 1Gbps throughput• 200m to 5km range• Solutions start under $10,000

Leased Systems

• More common in metropolitan areas• Monthly service fee with little/no customer

intervention• Typically much larger (shared) bandwidth

available• Can become saturated during large scale

outages that impacts multiple customers

Discussion Topics

• Security of LoS solutions• Protection of LoS systems• Tower/roof rights• Use of relaying

Security of LoS solutions

• Most LoS is considered “private network” and difficult to remotely compromise

• Very susceptible to physical compromise• Beware of shared/co-used transmission sites

(roof tops, shared towers, ect)

Protection of LoS Systems

• Environmental and weather conditions can have heavy impact on reliability

• Monitoring systems are critical

Tower and Roof Rights

• Any tower/roof rights should be secured in writing

• Seaming LoS obstacles may be best transmission sites

• Backup connectivity can often be shared among tenants in order to secure rights and lower cost

LoS Relaying

• LoS relaying is often used to extend range and circumvent obstacles

• Increased points of failure