• Time Slot Definition Wikipedia Dictionary
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After production, the show is handed over to the television network, which sends it out to its affiliate stations, which broadcast it in the specified broadcast programming time slot. If the Nielsen ratings are good, the show is kept alive as long as possible. If not, the show is usually canceled. The show's creators are then left to shop. Time slot management offers the possibility of offering different types of time slots. For example, with allocation, the type of goods, the contract details, the carrier can be taken into account to accommodate more flexible and varying requirements. As such, regular time slots have delivery dates for specific carriers. Time slot definition: A television or radio programme's time slot is the time when it is broadcast. Meaning, pronunciation, translations and examples. Simultaneous substitution (also known as simsubbing or signal substitution) is a practice mandated by the Canadian Radio-television and Telecommunications Commission (CRTC) requiring broadcast distribution undertakings (BDUs) in Canada to distribute the signal of a local or regional over-the-air station in place of the signal of a foreign or non-local television station (typically one that is. Number one in the time slot. I had my own show in the coveted time slot; The parameters shall be provided to the airport coordinator in good time before the initial slot allocation takes place for the purpose of scheduling conferences. I guess I could reconsider the time slot in exchange for your. The time; slots concerned are the same as those.

Time-division multiple access (TDMA) is a channel access method for shared-medium networks. It allows several users to share the same frequency channel by dividing the signal into different time slots.^[1] The users transmit in rapid succession, one after the other, each using its own time slot. This allows multiple stations to share the same transmission medium (e.g. radio frequency channel) while using only a part of its channel capacity. Dynamic TDMA is a TDMA variant that dynamically reserves a variable number of time slots in each frame to variable bit-rate data streams, based on the traffic demand of each data stream.

TDMA is used in the digital 2Gcellular systems such as Global System for Mobile Communications (GSM), IS-136, Personal Digital Cellular (PDC) and iDEN, and in the Digital Enhanced Cordless Telecommunications (DECT) standard for portable phones. TDMA was first used in satellite communication systems by Western Union in its Westar 3 communications satellite in 1979. It is now used extensively in satellite communications,^[2][3][4][5]combat-net radio systems, and passive optical network (PON) networks for upstream traffic from premises to the operator.

TDMA is a type of time-division multiplexing (TDM), with the special point that instead of having one transmitter connected to one receiver, there are multiple transmitters. In the case of the uplink from a mobile phone to a base station this becomes particularly difficult because the mobile phone can move around and vary the timing advance required to make its transmission match the gap in transmission from its peers.

Characteristics[edit]

• Shares single carrier frequency with multiple users
• Non-continuous transmission makes handoff simpler
• Slots can be assigned on demand in dynamic TDMA
• Less stringent power control than CDMA due to reduced intra cell interference
• Higher synchronization overhead than CDMA
• Advanced equalization may be necessary for high data rates if the channel is 'frequency selective' and creates Intersymbol interference
• Cell breathing (borrowing resources from adjacent cells) is more complicated than in CDMA
• Frequency/slot allocation complexity
• Pulsating power envelope: interference with other devices

In mobile phone systems[edit]

2G systems[edit]

Most 2G cellular systems, with the notable exception of IS-95, are based on TDMA. GSM, D-AMPS, PDC, iDEN, and PHS are examples of TDMA cellular systems.

Time Slot Definition Wikipedia Dictionary

In the GSM system, the synchronization of the mobile phones is achieved by sending timing advance commands from the base station which instructs the mobile phone to transmit earlier and by how much. This compensates for the propagation delay resulting from the light speed velocity of radio waves. The mobile phone is not allowed to transmit for its entire time slot, but there is a guard interval at the end of each time slot. As the transmission moves into the guard period, the mobile network adjusts the timing advance to synchronize the transmission.

Initial synchronization of a phone requires even more care. Before a mobile transmits there is no way to actually know the offset required. For this reason, an entire time slot has to be dedicated to mobiles attempting to contact the network; this is known as the random-access channel (RACH) in GSM. The mobile attempts to broadcast at the beginning of the time slot, as received from the network. If the mobile is located next to the base station, there will be no time delay and this will succeed. If, however, the mobile phone is at just less than 35 km from the base station, the time delay will mean the mobile's broadcast arrives at the very end of the time slot. In that case, the mobile will be instructed to broadcast its messages starting nearly a whole time slot earlier than would be expected otherwise. Finally, if the mobile is beyond the 35 km cell range in GSM, then the RACH will arrive in a neighbouring time slot and be ignored. It is this feature, rather than limitations of power, that limits the range of a GSM cell to 35 km when no special extension techniques are used. By changing the synchronization between the uplink and downlink at the base station, however, this limitation can be overcome.^{[citation needed]}

3G systems[edit]

Although most major 3G systems are primarily based upon CDMA,^[6] time-division duplexing (TDD), packet scheduling (dynamic TDMA) and packet oriented multiple access schemes are available in 3G form, combined with CDMA to take advantage of the benefits of both technologies.

While the most popular form of the UMTS 3G system uses CDMA and frequency division duplexing (FDD) instead of TDMA, TDMA is combined with CDMA and time-division duplexing in two standard UMTS UTRA.

In wired networks[edit]

The ITU-TG.hn standard, which provides high-speed local area networking over existing home wiring (power lines, phone lines and coaxial cables) is based on a TDMA scheme. In G.hn, a 'master' device allocates 'Contention-Free Transmission Opportunities' (CFTXOP) to other 'slave' devices in the network. Only one device can use a CFTXOP at a time, thus avoiding collisions.FlexRay protocol which is also a wired network used for safety-critical communication in modern cars, uses the TDMA method for data transmission control.

Comparison with other multiple-access schemes[edit]

In radio systems, TDMA is usually used alongside frequency-division multiple access (FDMA) and frequency division duplex (FDD); the combination is referred to as FDMA/TDMA/FDD. This is the case in both GSM and IS-136 for example. Exceptions to this include the DECT and Personal Handy-phone System (PHS) micro-cellular systems, UMTS-TDD UMTS variant, and China's TD-SCDMA, which use time-division duplexing, where different time slots are allocated for the base station and handsets on the same frequency.

A major advantage of TDMA is that the radio part of the mobile only needs to listen and broadcast for its own time slot. For the rest of the time, the mobile can carry out measurements on the network, detecting surrounding transmitters on different frequencies. This allows safe inter frequency handovers, something which is difficult in CDMA systems, not supported at all in IS-95 and supported through complex system additions in Universal Mobile Telecommunications System (UMTS). This in turn allows for co-existence of microcell layers with macrocell layers.

CDMA, by comparison, supports 'soft hand-off' which allows a mobile phone to be in communication with up to 6 base stations simultaneously, a type of 'same-frequency handover'. The incoming packets are compared for quality, and the best one is selected. CDMA's 'cell breathing' characteristic, where a terminal on the boundary of two congested cells will be unable to receive a clear signal, can often negate this advantage during peak periods.

A disadvantage of TDMA systems is that they create interference at a frequency which is directly connected to the time slot length. This is the buzz which can sometimes be heard if a TDMA phone is left next to a radio or speakers.^[7] Another disadvantage is that the 'dead time' between time slots limits the potential bandwidth of a TDMA channel. These are implemented in part because of the difficulty in ensuring that different terminals transmit at exactly the times required. Handsets that are moving will need to constantly adjust their timings to ensure their transmission is received at precisely the right time, because as they move further from the base station, their signal will take longer to arrive. This also means that the major TDMA systems have hard limits on cell sizes in terms of range, though in practice the power levels required to receive and transmit over distances greater than the supported range would be mostly impractical anyway.

Dynamic TDMA[edit]

In dynamic time-division multiple access (dynamic TDMA), a scheduling algorithm dynamically reserves a variable number of time slots in each frame to variable bit-rate data streams, based on the traffic demand of each data stream. Dynamic TDMA is used in

• HIPERLAN/2 broadband radio access network.
• IEEE 802.16a WiMax
• Military Radios / Tactical Data Link

See also[edit]

• Channel access method (CAM)
• Duplex (telecommunications) (FDD, TDD)

Time Slot Definition Wikipedia Francais

References[edit]

1. ^Guowang Miao; Jens Zander; Ki Won Sung; Ben Slimane (2016). Fundamentals of Mobile Data Networks. Cambridge University Press. ISBN978-1107143210.
2. ^Maine, K.; Devieux, C.; Swan, P. (November 1995). Overview of IRIDIUM satellite network. WESCON'95. IEEE. p. 483.
3. ^Mazzella, M.; Cohen, M.; Rouffet, D.; Louie, M.; Gilhousen, K. S. (April 1993). Multiple access techniques and spectrum utilisation of the GLOBALSTAR mobile satellite system. Fourth IEE Conference on Telecommunications 1993. IET. pp. 306–311.
4. ^Sturza, M. A. (June 1995). Architecture of the TELEDESIC satellite system. International Mobile Satellite Conference. 95. p. 214.
5. ^'ORBCOMM System Overview'(PDF).
6. ^K. Jagannatham, Aditya (2016). Principles of Modern Wireless Communication Systems. McGraw-Hill Education. ISBN9789339220037.
7. ^'Minimize GSM buzz noise in mobile phones'. EETimes. July 20, 2009. Retrieved November 22, 2010.

Slot time is a concept in computer networking. It is at least twice the time it takes for an electronic pulse (OSILayer 1 - Physical) to travel the length of the maximum theoretical distance between two nodes. In CSMA/CD networks such as Ethernet, the slot time is an upper limit on the acquisition of the medium, a limit on the length of a packet fragment generated by a collision, and the scheduling quantum for retransmission.^[1]

Time Slot Definition Wikipedia Encyclopedia

Since a pulse's runtime will never exceed slot time (the maximum theoretical time for a frame to travel a network), the network interface controller, or NIC waits a minimum of slot time before retransmitting after a collision happened, in order to allow any pulse that was initiated at the time that the waiting NIC was requested to send, to reach all other nodes. By allowing the pulse to reach the waiting NIC, a local collision occurs (i.e. while still sending) rather than a late collision occurring (after sending may or may not have ended). By having the collision occur at the NIC (local) and not on the wire (late) CSMA/CD implementation recover the situation by retransmitting later.

Some times for Ethernet slot time include:^[2]

See DIFS for information on 802.11x slot times.

References[edit]

1. ^IEEE 802.3 4.2.3.2.3 Collision handling
2. ^IEEE 802.3 4.4.2 MAC parameters
3. ^Slot time is only applicable to half-duplex transmissions. Since slot time is the time required to wait for the medium to be free from transmissions, there is no time required to wait for full-duplex transmissions. 1 Gbit/s (in practice) and faster (by standard) are full duplex technologies, so slot time is not applicable here.
4. ^theoretical, only full-duplex devices exist