Advances in the Technologies of Transmission Media

Advances in the Technologies of Transmission Media

ABSTRACT

There are two main factors which decide the success of any cabling system or transmission media – a) performance and b) economics (including the ease of installation). Today optical fibers and shielded twisted pair systems are better than unshielded twisted pair systems because of greater robustness and greater signal headroom. We present the state of art, talking about the recent and major technologies in the transmission media used today. We talk about the current and future trends for transmission media, what the future for technologies for transmission media might look like. We throw some light on key industrial players in this field and what innovations are being carried out, by stating some case studies. We investigate the weaknesses of transmission media obstructing their success.

1. INTRODUCTION

Transmission media is a trail that carries the information from sender to receiver. We make use of different type of cables or waves to transmit data. Data is transmitted normally through electrical or electromagnetic signals [1].

An electrical signal is in the form of current. An electromagnetic signal is sequence of electromagnetic energy pulses at various frequencies. These signals can be transmitted through optical fibers, copper wires, atmosphere, vacuum and water [1].

Transmission media is broadly classified into two groups (figure 1).

Guided or Wired Media or Bound Transmission Media [1]: Bound transmission media are the cables that are tangible or have physical existence. Popular bound transmission media in use are twisted pair cable, co-axial cable and fiber optical cable. Each of them has its own characteristics like transmission speed, effect of noise, physical appearance, cost etc. 

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Unguided or Wireless Media or Unbound Transmission Media [1]: Unbound transmission media are the ways of transmitting data without using any cables. Currently, wireless communication is becoming popular. Wireless LANs are being installed in office and college campuses. This transmission uses Radio, Microwave wave, Infra-red are some of popular unbound transmission media.

Figure 1: Types of Transmission Media [1]

II. STATE OF ART

A. Unshielded Twisted Pair

Currently, there are attempts being made for solidifying the standards for UTP transmission characterization to extend it to 250 MHz.[2] There are many obstacles that would needed to be solved for this, but one can expect that hurdles will get resolved, both politically and technically. But the viability of UTP remains in question for the increased information speeds. In future, the efficiency of bandwidth utilization must beimproved, or else, the electronics costs, installation and testing may fade the benefits of UTP compared to other options.

B. Shielded Twisted Pair

The transmission characterization of STP currently is to 300 MHz[2]. Although STP is exceptionally good as a transmission medium, it is limited to special situations and certain nations because of the material and installation costs. Just like UTP, bandwidth limit has not been reached for STP. So, the major factor deciding the adaption of STP could be economics.

C. Glass Optical Fibre

Many organizations and techies have regarded optical fibres to be ultimate future proofing media for many years. The distance limits and bandwidth capacity for optical fibres were not challenged or questioned by high speed applications, until the arrival of 1000 Mbps ethernet. While on one hand, the new 62.5/125-micron fibre will be costlier than single mode fibre, on the other hand 50/125-micron multimode optical fibre also have disadvantages being more bend-sensitive and having greater loss at connectors compared to 62.5/125 micron fibre. So there is no such thing as universal future proof media [2].

D. Fibre Optic WDM

For expanding the optical fibre data carrying capacity, Wave Division Multiplexing is a solution, which eradicates the need for new media type being used. For increasing the data carrying capacity of optical fibres, WDM splits the laser light carrying the data through optical fibre glass into different wavelengths. Each of these wavelengths carry a discrete data channel. As of now, 40 different wavelengths are supported by technology, but in the near future, this can be expanded to 128 wavelengths. The advantage of WDM is that the there is no need for additional fibres and existing fibres and connectors can be used with this technology [2]

E. Plastic Optical Fibre

Earlier, POF were restricted to low speed and short distance applications. But today, the bandwidth has been increased to 3GHz/100m due to technical advancements of POF in the graded index. Recent developments in the single mode POF have made it possible for POF to be considered realistically for high speed applications such as SONET, FDDI, Escon, fibre channel, Asynchronous transfer Mode etc. But due to the restriction of current technology to 50-meter distance at required bandwidth, no standard body endorse this medium. Perhaps, it could be 5 years before the commercial availability of low cost POF [2].

F. Coaxial

Coaxial cable is the most used choice of transmission medium for wideband applications including high fidelity audio, television, baseband and broadband communications. Coaxial networks are capable of supporting higher bandwidths than UTP and operating with less sophisticated electronics compared to UTP. For higher bandwidth applications, coaxial cables could outperform UTP in terms of costs, maintenance and testing [2].

III. CURRENT AND FUTURE TRENDS

A. Overhead lines

These lines are being used since the start in transmission networks. To accommodate higher temperature ratings and high currents, new conductors like Aluminium conductor steel supported(ACSS), Aluminium conductor composite reinforced(ACCR), Aluminum conductor composite core(ACCC) have wider range than conventionally used Aluminium conductor steel reinforced(ACSR). Higher temperature conductors have 30% greater capacity and lower sag (Figure 2). These new conductors are capable of withstanding higher temperatures and thus higher amount of current can be carried by these. For these conductors, lesser towers are needed because of lower sag.

Figure 2. Sag comparison at 180 degrees Celsius [2]

B. Onshore Cable Technology

Maximum voltage in Europe currently is 420kV. The transmission network voltage of Europe is expected to stay in the same range of 380-420kV in the near future. But in the times ahead, for overcoming public acceptance and to obtain building permits, one of the possible solutions expected is to partially underground HVAC cable lines. There is a likely increase of current rating above 1.8kA, for typical partial under grounding solution.

C. Offshore Cable Technology

For submarine connections, one of the commonly used cables are HVAC extruded insulation cables. They can have a single core configuration or three core configurations. For these cables, the maximum transmission voltage is 550kV. For extruded XLPE HVAC subsea cables, a similar technical evolution looking at the 2050 horizon as for XLPE HVAC underground cables can be expected [3]. Also, there is an expected increase in the depth of submarine HVAC cables installation to over 2500m in the future compared to several meters today.

D. Gas Insulated Lines

In the areas where installation of power cables and/or overhead lines is nearly impossible, alternative is gas insulated lines (GIL). These lines provide high capacity transfer and are used in the areas where maximum electromagnetic field is limited by technological requirements or governmental regulations. In the areas where flammable material is absent like tunnel installation for hydropower plants or under the cities, GIL are widely applied. There is an expected increase of GILs in the near future due to an increase in the limitations regarding rights of way for areas which are densely populated. GILs can find use in many areas above the ground, tunnels, trenches, apart from being directly buried.

IV. KEY INNOVATIONS

1. Guided Transmission Media

1.1.  Twisted Pair

The twisted-pair cable is a common and most widely used guided transmission medium. It consists of two insulated copper wires arranged in a regular spiral pattern. A pair of these wires acts as a single communication link and are usually bundled in numbers together, wrapped in a tough protective sheath to form a cable. When used on long-distance links, the twist length typically varies from 5-15 cm. The thickness of the wires in a pair is from 0.4-0.9 mm. The twisted pair transmission medium is applied for telephone network, and both analog and digital signals [4]. They provide a conduit from one device to another [5]. Twisted pair is of two types: unshielded and shielded. Unshielded twisted pair (UTP) refers to ordinary telephone wire. The shielded twisted pair (STP) is an improvement of the untwisted shifted pair (UTP) where a metallic braid or sheathing that reduces interference is used [4].

Figure 3. Twisted-pair cable [5]

Figure 4. a) Unshielded twisted pair (UTP), b) Shielded twisted pair (STP) [5]

1.2  Coaxial Cable

The coaxial cable consists of two conductors working and they operate over wider range of frequencies compared to the twisted pair. It is made up of an outer cylindrical conductor surrounding a single inner wire conductor (Figure 2.0) [4]. Generally, coaxial cable is widely applied in distribution of over dozens of cable TV signals (TV channels) to homes and offices, long-distance telephone transmission, short-run computer systems links, and local area networks (LAN). It is also used to transmit both analog and digital signals [4].

Figure 5. Coaxial cable [5]

1.3  Optical Fibre

Optical fibre is a key technological innovation in data transmission. It is widely used in long-distance telecommunications due to its greater capacity, smaller size and lighter weight, lower attenuation, electromagnetic isolation, and great repeater spacing [4]. The following five categories are useful for optical fibre:

a) Long-haul trunks: 150km in length (20,000-60,000 voice channels)

b) Metropolitan trunks: average 12km length and are usually installed underground

c) Rural exchange trunks: 40-160 km circuits length (fewer than 5000 voice channels)

d) Subscriber loops: They are fibers that run directly to a subscriber from the central exchange.

e) Local area networks: 100 Mbs – 10 Gbps capacity.

Figure 6 Optical fibre [5]

2.  Unguided Wireless Transmission

2.1  Antennas

An electrical conductor used for radiating or collecting electromagnetic energy is called an antenna. The antenna can function as a transmitter where electrical energy is converted into electromagnetic energy by the antenna, and it can function as a receptor where electromagnetic energy striking on the antenna is converted into electrical energy and fed into the receiver [4]. The parabolic antenna is used in terrestrial microwaves, line of sight communication, frequencies within 10-60 GHz, and in higher frequencies for higher data rates [6].

Figure 7. Satellite Antenna and Dish Antenna [5]                                                                                                  

2.2  Terrestrial Microscope

This is a common type of microwave antenna about 3 m in diameter, located at substantial heights above ground level and used in long haul communications service. It is applied in cellular systems, wireless LANs, telephone and voice and data transmission as an alternative to both voice and television transmission [4].

2.3  Satellite Microwave

This is a stationary satellite that serves as the link between two or more ground-based microwave transmitter/receivers also called ground stations. It functions in two ways by first providing a point-to-point link between two distant ground-based antennas and secondly providing communication between a ground-based transmitter and several ground-based receivers. It is widely suitable to television distribution, long-distance telephone transmission and private business networks [4].

2.4  Broadcast Radio

Radio frequencies range from 3kHz-300GHz, and this range is used for broadcast transmissions, FM radio and a number of data networking applications.

2.5  Infrared

Generally, the infrared signals are used for short range communication is closed areas using line-of-sight propagated transmitters/receivers (transceivers) [5].

3.  Wireless Propagation

3.1  Ground Wave Propagation

As the name implies, ground waves propagation follows the contour of the earth, propagating over considerable distances. It is considerably noted in frequencies up to about 2MHz. a typical example is the AM radio [4]

3.2  Sky Wave Propagation

In sky wave propagation mode, the sky wave signals usually travel through a number of hops, bouncing back and forth between the ionosphere and the earth’s surface. This allows for the possibility of a signal to be picked up thousands of kilometres from the transmitter.

3.3  Line of Sight Propagation

This propagation operates in frequencies above 30 MHz where neither ground wave nor sky wave can propagate. For the satellite communication, any signal above 30 MHz can be transmitted between an earth station and a satellite overhead not beyond the horizon while, for the ground-based communication, line of sight must be observed between the transmitting and receiving antennas [4].  Optical line of sight can be expressed mathematically as:

$d=3.57\surd h$

Where d is the distance between an antenna and the horizon in kilometers and h is the antenna height in meters.

Radio line of sight to the horizon is expressed mathematically as:

$d=3.57\surd \mathit{Kh}$

Where K is an adjustment factor accounting for the refraction [5].

V. KEY INDUSTRIAL PLAYERS

In this section of the paper, we will briefly highlight and

discuss the key industry players at the forefront of high bandwidth transmission media. In the grand scheme of things, all the companies providing high bandwidth transmission media as a service do this with the singular aim of providing a dynamically scalable

infrastructure for application, data and file storage.

There are a lot of industry players in the transmission media sphere but for this paper, we will discuss just five major players.

4.1  Siemon Company

Siemon is a key industrial leader specializing in the manufacture and innovation of high quality, high-performance network cabling solutions (copper and fibre cabling systems). The Siemon Labs are heavily involved in Research and Development (R&D) of industry standards high performance network infrastructure solutions [7].

4.2  Asea Brown Boveri (ABB)

Asea Brown Boveri (ABB) is a power and automation technological company focusing on power transmission, distribution and power plant automation that serves electricity, gas and water utilities to its customers as well as industrial and commercial customers [8].

.

4.3  GE Energy (General Electric Energy)

One of the world’s leading suppliers of power generation and energy delivery technologies. GE Energy operates in all areas of the transmission and energy industry. They provide corporate-wide initiative to aggressively provide solutions and services to maximize transmission system reliability and efficiency [8][9].

4.4  KEC International Ltd.

This is India’s second largest manufacturer of electric power transmission towers in the areas of infrastructure engineering, procurement and construction (EPC). KEC has presence in the verticals of Power transmission and Distribution, Cables, etc. [8][10]

4.5  General Cable Corporation

General Cable, A company of the Prysmian Group is a global leader in the energy and telecom cable systems industry [10]. They deal in the development, design, manufacture, marketing and distribution of copper, aluminum, and fiber optic and cable products for the energy, industrial, specialty and communications markets around the world [8] [11]. The group strongly operates in the business of underground and submarine cables and systems for power transmission and distribution, of special cables for applications in many different industries and of medium and low voltage cables for the construction and infrastructure sectors In telecommunications industry, the Group manufactures cables and accessories for voice, video and data transmission, in  the range of optical fibre, optical and copper cables and connectivity systems [11].

VI. CHALLENGES

Transmission media are the corporeal infrastructure components that hold data from one computer to another. Transmission media can be categorized into guided and unguided-guided media [12].

Though there are many transmission medias, all of them have challenges when being used. They are classified into:

Guided Transmission Media [13]:

• Twisted pair cables have high attenuation; making them incapable of carrying signals over a long distance without the use of repeaters.
• Twisted pair cables have low bandwidth; thus, they cannot be used for broadband connection.
• Coaxial cables are expensive and thick thus making it difficult to work with them.
• Optical fibers have installation problems; they are very fragile and need special care to make them sufficiently robust for an office environment.
• They have noise immunity; thus, it is impossible to virtually tap. To tap the fiber must be cut and a detector must be inserted.
• Optical fibers are difficult to solder, expensive and the connection losses are common.

Unguided Transmission Media [14]:  

• Multipath Propagation: When a signal goes from A to B the signal can be reflected or refracted by different interacting objects in the environment. Thus, making the propagation path very large.
• Spectrum Limitation: The spectrum available for wireless communication is limited and regulated by international agreements. Thus, this spectrum must be used in a highly efficient manner.
• Energy Limitation: Wireless communication require the mobile station to use power by one-way or rechargeable batteries to transmit information over the air.
• User Mobility: The system must know which cell the user is in. If the user moves across the cell boundary a different BS becomes the serving BS. This should not affect the user communication.
• Noise Limited System: If the user moves away from the base station, the received signal power decreases, and at a certain distance, the SNR does not achieve the required threshold for reliable communication. Therefore, the range of the system is noise limited and equivalently signal power limited.

VII. CASE STUDY

Swisscom and Ge’s smallworld: Meeting the growing demand for higher bandwidth service

Swisscomm, Switzerland’s leading telecommunications provider that offers a full spectrum of services including television, internet, and mobile and fixed line telephone network was faced with a rapidly expanding network without having a single view to its physical inventory, making it hard to plan and scale the network. The company’s network documentation existed in hard copy only, with limited digital data available. They had more than 30,000 schematic plans, 110,000 situation plans and one million splicing sketches. This extensive network documentation was difficult to manage, and data integrity was increasingly hard to maintain. The solution Swisscomm needed was a scalable solution to share specified data with other utilities and third-party network operators as mandated by their laws [15]. Swisscomm brought in GE’s Smallworld Physical Network Inventory to model the entire physical network for copper and fibre networks, supporting multiple communications technologies and equipment from vendors equipped with the ability to interface with an array of IT systems, allowing end-to-end business process integration [10].

Swisscomm’s Planning Tool for Access Networks (PTA) application is a Smallworld-based Network Inventory Portfolio solution that supports network construction projects lifecycle and network asset inventory of Swisscomm including all physical outside plant asset such as cables, conduits, cabinets, copper and fibre optics. Smallworld solution from design to building to operations allows designs to be optimized to create the lowest cost network to build, the optimized designs are automatically transferred into PTA to complete the detailed engineering work required to complete the design thereby bringing delivering market products at a faster rate. The NetCracker, an integral system of Swisscomm that provides the inventory of the logical fibre network was synchronised with Smallworld solution to address quality checks in data and spot errors well in advance.

Swisscomm continually looks for solutions to address the need for network expansion (higher bandwidth) as its demands became higher and critical. Therefore, the introduction of the Smallworld product portfolio provided a common database for the full view into the physical network inventory, efficient use and allocation of resources and overall improvement and rationalization of Swisscom internal processes [15]

VIII CONCLUSION

In summary, transmission media are essential for communication systems. The transmission characteristics of the medium in use are important because they directly affect the communication quality. Guided Media have advantages as well as disadvantages. Media’s like twisted cables can be used in short communications like telephone lines and not for broadband, coaxial cables have greater bandwidth and used in broadband but are heavy and expensive, optical fibers have less attenuation, light weight but require too much maintenance. Unguided Media may seem to be advantages over guided media, but it also has liabilities like, the data sharing is upon international agreements and signal range matters, as in the user must be in a certain range to get a strong signal and the base station switching must take place without effecting the communication. Thus, by using the researches mentioned transmission medias can be improved.

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