What is an Uplink and Downlink ?

The uplink and the downlink are the terminologies that are used in the satellite communications. The data when sent from the ground to the satellite is called the uplink and data when sent from satellite to ground is called downlink. The uplink and the downlink process goes in parallel and this is also a two way communication.

The uplink and downlink services are provided by various companies for the use of television network or the internet network. The uplink and downlink can also be referred to the cell phone and the tower of service provider, the data that goes from the tower to the cell phone is the downlink segment and the data that goes from the cell phone to the tower is the uplink segment.

What is an Uplink?

• The communication between the earth channel transmitter and the satellite is called the uplink.
• The satellite uplink is usually where the earth channel transmits signals and satellite receives it.
• The uplink frequency ranges from 5.9 GHz to 6.4 GHz.
• The conventional Ku-band that is used for the satellite communication in Europe has the uplink frequency range of 14.0 to 14.5 GHz.
• In the case of a radio-communication service, an uplink is used to transmit signals from a global station to a radio station or a high-altitude platform.
• For global service module (GSM) and mobile networks, radio radiated uplink is a method of transferring from a portable station (mobile phone) to a base station (mobile domain).

What is a Downlink?

• The connection between the satellite to the receiver of the earth channel is known as the downlink frequency.
• The downlink frequency of a satellite is the frequency at which the satellite transmits the signal and the earth receives it.
• Downlink frequency in case of satellite ranges from 3.7 GHz to 4.2 GHz.
• The conventional Ku-band that is used for the satellite communication in Europe has the downlink frequency range of 11.70 to 12.20 GHz.
• In the case of a radio-communication service, the downlink is used to transmit signals from a radio station, or a high-altitude platform to a global station.
• In the case of satellite communications, the downlink is a satellite link from the base station. For mobile networks, radio downlink is a method of transferring signal from a mobile allocation to a cell phone.

What are Uplink and Downlink in mobile telecommunication?

Mobile signal booster boosts weak mobile signal within a building and it allows you to get faster data speeds and enhance communication strength. Uplink and downlink, also called upload and download, refer to the two connections between a mobile tower and a phone.

The speed of uplink bandwidth and downlink bandwidth are not equal, usually, the speed of upload is less than the speed of the download.

While having conversation one must have clear conversation over the cell phone and there must not be any kind of distortion from any side. Disruption of the downlink or uplink during the mobile connection causes connectivity issues. Years ago, this was especially true because the 3g mobile signal included uplink and downlink frequency bands in the range 850 and 1900 MHz.

What are Uplink and Downlink in satellite communication?

Satellite links are used to provide connections between very large distances also called the global broadcasting. This is achieved by using a satellite as a repeater. The channel below transmits the signal upwards that is towards the satellite with a frequency known as the uplink frequency. The satellite receives this signal and it also broadcasts it with a downlink frequency to another sub-channel. If a digital communication signal is used, the signal may be regenerated before it is transmitted back to earth.

The satellite receives a radio signal from its uplink receiver. Then sends this signals to the group with downlink frequency, the signal is amplifier before sending back to the ground that is to the transmission antenna. These operations are performed via satellite transponder.

At present, there are four main antennas used in communication satellites: telephone antennas, horn antennas, optical reflectors antennas and many more.

The satellite communication system can be further divided into 2 parts:

Space segment

The space segment includes satellites and low-level resources like telemetry tracking and commands. The space segment of the synthetic satellite system is one of its three functional components the other two includes the transmitter on the ground and the user. The communications satellite is built with a paid communications loader (repeater and antenna) and a supportive spacecraft bus (including solar array and batteries, attitude and Orbital systems, building and temperature control system), and is orbital by the launch vehicle.

Earth segment

The earth segment includes the transmitter and the commanding unit. The transmitting unit consists of the transmitter to send the signal to the satellite using uplink. Various companies can rent the ground segment instead of building their own, like in case of the television industry. The earth segment also include commanding unit that include that is used govern the operation of the satellite on the earth. A satellite can be assigned a particular Earth segment so that the satellite follows it only throughout 24 hours.

Uses of the Uplink and Downlink segment

• The same antenna is used for transmitting and receiving.
• The uplink and downlink frequency bands are separated in batches to prevent rotation in the satellite amplifier while simultaneously transmitting and receiving.
• In addition, low-frequency bands are used in the downlink to take advantage of low atmospheric losses, thereby reducing the amplifier requirements for satellite power.
• The upstream port is used to connect the device to other high-speed devices in the topology or to connect to a small area network through a large network.
• The uplink power source is still distributed among users, while in the downlink, the power resource is allocated in the base channel. In addition, the high uplink transmission capacity of a single device is usually much lower than the output capacity of the base channel.

Common Mistakes

Uplink and downlink splitting in high-load wireless communication systems depends on the service provider and the number of users with high traffic density.

Context and Applications

In each of the expert exams for undergraduate and graduate publications, this topic is huge and is mainly used for:

• Bachelor of technology in the Electrical and Electronic department
• Bachelor of Science in Physics
• Master of Science in Physics

Related Concepts

• Satellite communication.
• Radar communication

Practice Problems

Q1  The downlink frequency is lower than the uplink frequency.

(a) True

(b) False

Correct option- (b)

Explanation- The original signal transmitted from the earth station to the satellite is called the uplink, and the signal transmitted from the satellite to the receiving station is called the downlink. The downlink frequency is higher than the uplink frequency.

Q2  After the up-linking process, a satellite _____ and _____ the signal.

(a) receives, amplifies

 (b) amplifies, receives

 (c) receives, adds noise

 (d) adds noise and transmits

Correct option- (a)

Explanation- A standard satellite link involves the transmission or promotion of a signal from an earth station to a satellite. The satellite then detects and amplifies the signal and transmits it to earth, where it detects and reconfigure the earth's channels and terminals.

Q3  Uplink frequency range is from ____

(a) 2.9 to 3.4 GHz

 (b) 3.9 to 4.4 GHz

 (c) 5.9 to 6.4 GHz

 (d) 6.9 to 7.4 GHz

Correct option- (c)

Explanation- Uplink frequency range is 5.9 to 6.4 GHz. A radio frequency (RF) unit called an upconverter is used to convert the base-band frequency into an RF to be transmitted as an Uplink.

Q4  Downlink frequency range ___________.

(a) 2.7 to 3.2 GHz

 (b) 3.7 to 4.2 GHz

 (c) 5.9 to 6.4 GHz

 (d) 6.9 to 7.4 GHz

Correct option- (b)

Explanation- Downlink frequency range is 3.7 to 4.2 GHz. A radio frequency unit called as downconverter is used to convert radio frequency to baseband frequency for the reception on the downlink side.

Q5  The uplink frequency is usually used to transmit signals from a earth channel transmitter to a satellite.

(a) True

(b) False

Correct option- (a)

Explanation- The frequency of uplink is usually present as the Earth's channel communicating with a satellite. The satellite transponder converts this signal to another frequency and sends it to a second Earth station.