Existing last mile delivery systems Last mile

1 existing last mile delivery systems

1.1 wired systems (including optical fiber)

1.1.1 local area networks (lan)
1.1.2 telephone
1.1.3 catv
1.1.4 optical fiber


1.2 wireless delivery systems

1.2.1 lightwaves , free-space optics
1.2.2 radio waves
1.2.3 one-way (broadcast) radio , television communications
1.2.4 two-way wireless communications
1.2.5 satellite communications
1.2.6 broadcast versus point-to-point


1.3 intermediate system
1.4 line aggregation

existing last mile delivery systems
wired systems (including optical fiber)

wired systems provide guided conduits information-carrying energy (ice). have degree of shielding, limits susceptibility external noise sources. these transmission lines have losses proportional length. without addition of periodic amplification, there maximum length beyond of these systems fail deliver adequate s/n ratio support information flow. dielectric optical fiber systems support heavier flow @ higher cost.

local area networks (lan)

traditional wired local area networking systems require copper coaxial cable or twisted pair run between or among 2 or more of nodes in network. common systems operate @ 100 mbit/s, , newer ones support 1000 mbit/s or more. while length may limited collision detection , avoidance requirements, signal loss , reflections on these lines define maximum distance. decrease in information capacity made available individual user proportional number of users sharing lan.

telephone

in late 20th century, improvements in use of existing copper telephone lines increased capabilities if maximum line length controlled. support higher transmission bandwidth , improved modulation, these digital subscriber line schemes have increased capability 20-50 times compared previous voiceband systems. these methods not based on altering fundamental physical properties , limitations of medium, which, apart introduction of twisted pairs, no different today when first telephone exchange opened in 1877 bell telephone company.

the history , long life of copper-based communications infrastructure both testament ability derive new value simple concepts through technological innovation – , warning copper communications infrastructure beginning offer diminishing returns continued investment. 1 of largest costs associated maintaining ageing copper infrastructure of truck roll - sending engineers physically test, repair, replace , provide new copper connections, , cost particularly prevalent in providing rural broadband service on copper. new technologies such g.fast , vdsl2 offer viable high speed solutions rural broadband provision on existing copper. in light of many companies have developed automated cross connects (cabinet based automated distribution frames) eliminate uncertainty , cost associated maintaining broadband services on existing copper, these systems incorporate form of automated switching , include test functionality allowing isp representative complete operations requiring site visit (truck roll) central office via web interface.

catv

community antenna television systems, known cable television, have been expanded provide bidirectional communication on existing physical cables. however, nature shared systems , spectrum available reverse information flow , achievable s/n limited. done initial unidirectional tv communication, cable loss mitigated through use of periodic amplifiers within system. these factors set upper limit on per-user information capacity, particularly when many users share common section of cable or access network.

optical fiber

fiber offers high information capacity , after turn of 21st century became deployed medium of choice ( fiber x ) given scalability in face of increasing bandwidth requirements of modern applications.

in 2004, according richard lynch, executive vice president , chief technology officer of telecom giant verizon, company saw world moving toward vastly higher bandwidth applications consumers loved broadband had offer , eagerly devoured as get, including two-way, user-generated content. copper , coaxial networks not – in fact, not – satisfy these demands, precipitated verizon s aggressive move fiber-to-the-home via fios.

fiber future-proof technology meets needs of today s users, unlike other copper-based , wireless last-mile mediums, has capacity years come, upgrading end-point optics , electronics without changing fiber infrastructure. fiber installed on existing pole or conduit infrastructure , of cost in labor, providing regional economic stimulus in deployment phase , providing critical foundation future regional commerce.

fixed copper lines have been subject theft due value of copper, optical fibers make unattractive targets. optical fibers cannot converted else, whereas copper can recycled without loss.

wireless delivery systems

mobile cdn coined term mobile mile categorize last mile connection when wireless systems used reach customer. in contrast wired delivery systems, wireless systems use unguided waves transmit ice. tend unshielded , have greater degree of susceptibility unwanted signal , noise sources.

because these waves not guided diverge, in free space these systems attenuated following inverse-square law, inversely proportional distance squared. losses increase more increasing length wired systems, loss increases exponentially. in free space environment, beyond given length, losses in wireless system lower in wired system.

in practice, presence of atmosphere, , obstructions caused terrain, buildings , foliage can increase loss above free space value. reflection, refraction , diffraction of waves can alter transmission characteristics , require specialized systems accommodate accompanying distortions.

wireless systems have advantage on wired systems in last mile applications in not requiring lines installed. however, have disadvantage in unguided nature makes them more susceptible unwanted noise , signals. spectral reuse can therefore limited.

lightwaves , free-space optics

visible , infrared light waves shorter radio frequency waves. use transmit data referred free-space optical communication. being short, light waves can focused or collimated small lens/antenna, , higher degree radio waves. thus, receiving device can recover greater portion of transmitted signal.

also, because of high frequency, high data transfer rate may available. however, in practical last mile environments, obstructions , de-steering of these beams, , absorption elements of atmosphere including fog , rain, particularly on longer paths, can restrict use last-mile wireless communications. longer (redder) waves suffer less obstruction may carry lower data rates. see ronja.

radio waves

radio frequencies (rf), low frequencies through microwave region, have wavelengths longer visible light. although means not possible focus beams tightly light, means aperture or capture area of simplest, omnidirectional antenna larger of lens in feasible optical system. characteristic results in increased attenuation or path loss systems not highly directional.

actually, term path loss of misnomer because no energy lost on free-space path. rather, merely not received receiving antenna. apparent reduction in transmission, frequency increased, artifact of change in aperture of given type of antenna.

relative last-mile problem, these longer wavelengths have advantage on light waves when omnidirectional or sectored transmissions considered. larger aperture of radio antennas results in greater signal levels given path length , therefore higher information capacity. on other hand, lower carrier frequencies not able support high information bandwidths, required shannon s equation when practical limits of s/n have been reached.

for above reasons, wireless radio systems optimal lower-information-capacity broadcast communications delivered on longer paths. high-information capacity, highly-directive point-to-point on short ranges, wireless light-wave systems useful.

one-way (broadcast) radio , television communications

historically, high-information-capacity broadcast has used lower frequencies, no higher uhf television region, television being prime example. terrestrial television has been limited region above 50 mhz sufficient information bandwidth available, , below 1,000 mhz, due problems associated increased path loss, mentioned above.

two-way wireless communications

two-way communication systems have been limited lower-information-capacity applications, such audio, facsimile, or radioteletype. part, higher-capacity systems, such two-way video communications or terrestrial microwave telephone , data trunks, have been limited , confined uhf or microwave , point-point paths.

higher capacity systems such third-generation cellular telephone systems require large infrastructure of more closely spaced cell sites in order maintain communications within typical environments, path losses greater in free space , require omnidirectional access users.

satellite communications

for information delivery end users, satellite systems, nature, have relatively long path lengths, low earth-orbiting satellites. expensive deploy , therefore each satellite must serve many users. additionally, long paths of geostationary satellites cause information latency makes many real-time applications unfeasible.

as solution last-mile problem, satellite systems have application , sharing limitations. ice transmit must spread on relatively large geographical area. causes received signal relatively small, unless large or directional terrestrial antennas used. parallel problem exists when satellite receiving.

in case, satellite system must have great information capacity in order accommodate multitude of sharing users , each user must have large antenna, attendant directivity , pointing requirements, in order obtain modest information-rate transfer. these requirements render high-information-capacity, bi-directional information systems uneconomical. 1 reason why iridium satellite system not more successful.

broadcast versus point-to-point

for terrestrial , satellite systems, economical, high-capacity, last-mile communications requires point-to-point transmission systems. except extremely small geographic areas, broadcast systems able deliver high s/n ratios @ low frequencies there not sufficient spectrum support large information capacity needed large number of users. although complete flooding of region can accomplished, such systems have fundamental characteristic of radiated ice never reaches user , wasted.

as information requirements increase, broadcast wireless mesh systems (also referred microcells or nano-cells) small enough provide adequate information distribution , relatively small number of local users require prohibitively large number of broadcast locations or points of presence along large amount of excess capacity make wasted energy.

intermediate system

recently new type of information transport midway between wired , wireless systems has been discovered. called e-line, uses single central conductor no outer conductor or shield. energy transported in plane wave which, unlike radio not diverge, whereas radio has no outer guiding structure.

this system exhibits combination of attributes of wired , wireless systems , can support high information capacity utilizing existing power lines on broad range of frequencies rf through microwave.

line aggregation

aggregation method of bonding multiple lines achieve faster, more reliable connection. companies believe adsl aggregation (or bonding ) solution uk s last mile problem.