Reservation ALOHA
Encyclopedia
Reservation ALOHA
, or R-ALOHA, is a channel access method
for wireless
(or other shared channel) transmission
that allows uncoordinated users to share a common transmission resource. Reservation ALOHA (and its parent scheme, Slotted ALOHA) is a schema or rule set for the division of transmission resources over fixed time increments, also known as slots
. If followed by all devices, this scheme allows the channel's users to cooperatively utilize a shared transmission resource—in this case, it is the allocation of transmission time.
Reservation ALOHA is an effort to improve the efficiency of Slotted ALOHA. The improvements with Reservation ALOHA are markedly shorter delays and ability to efficiently support higher levels of utilization. As a contrast of efficiency, simulations have shown that Reservation ALOHA exhibits less delay at 80% utilization than Slotted ALOHA at 20–36% utilization.
The chief difference between Slotted and Reservation ALOHA is that with Slotted ALOHA, any slot is available for utilization without regards to prior usage. Under Reservation ALOHA's contention-based
reservation schema, the slot is temporarily considered "owned" by the station that successfully used it. Additionally, Reservation ALOHA simply stops sending data once the station has completed its transmission. As a rule, idle slots are considered available to all stations that may then implicitly reserve (utilize) the slot on a contention basis.
Aloha
Aloha in the Hawaiian language means affection, peace, compassion and mercy. Since the middle of the 19th century, it also has come to be used as an English greeting to say goodbye and hello...
, or R-ALOHA, is a channel access method
Channel access method
In telecommunications and computer networks, a channel access method or multiple access method allows several terminals connected to the same multi-point transmission medium to transmit over it and to share its capacity...
for wireless
Wireless
Wireless telecommunications is the transfer of information between two or more points that are not physically connected. Distances can be short, such as a few meters for television remote control, or as far as thousands or even millions of kilometers for deep-space radio communications...
(or other shared channel) transmission
Transmission (telecommunications)
Transmission, in telecommunications, is the process of sending, propagating and receiving an analogue or digital information signal over a physical point-to-point or point-to-multipoint transmission medium, either wired, optical fiber or wireless...
that allows uncoordinated users to share a common transmission resource. Reservation ALOHA (and its parent scheme, Slotted ALOHA) is a schema or rule set for the division of transmission resources over fixed time increments, also known as slots
Slot time
Slot time is a concept in computer networking. It is twice the time it takes for an electronic pulse to travel the length ofthe maximum theoretical distance between two nodes...
. If followed by all devices, this scheme allows the channel's users to cooperatively utilize a shared transmission resource—in this case, it is the allocation of transmission time.
Reservation ALOHA is an effort to improve the efficiency of Slotted ALOHA. The improvements with Reservation ALOHA are markedly shorter delays and ability to efficiently support higher levels of utilization. As a contrast of efficiency, simulations have shown that Reservation ALOHA exhibits less delay at 80% utilization than Slotted ALOHA at 20–36% utilization.
The chief difference between Slotted and Reservation ALOHA is that with Slotted ALOHA, any slot is available for utilization without regards to prior usage. Under Reservation ALOHA's contention-based
Contention based protocol
A contention-based protocol is a communications protocol for operating wireless telecommunication equipment that allows many users to use the same radio channel without pre-coordination...
reservation schema, the slot is temporarily considered "owned" by the station that successfully used it. Additionally, Reservation ALOHA simply stops sending data once the station has completed its transmission. As a rule, idle slots are considered available to all stations that may then implicitly reserve (utilize) the slot on a contention basis.
See also
- Channel access methodChannel access methodIn telecommunications and computer networks, a channel access method or multiple access method allows several terminals connected to the same multi-point transmission medium to transmit over it and to share its capacity...
- Dynamic bandwidth allocationDynamic bandwidth allocationDynamic bandwidth allocation is a technique by which traffic bandwidth in a shared telecommunications medium can be allocated on demand and fairly between different users of that bandwidth. This is a form of bandwidth management, and is essentially the same thing as statistical multiplexing...
- General Packet Radio ServiceGeneral Packet Radio ServiceGeneral packet radio service is a packet oriented mobile data service on the 2G and 3G cellular communication system's global system for mobile communications . GPRS was originally standardized by European Telecommunications Standards Institute in response to the earlier CDPD and i-mode...
- Media Access ControlMedia Access ControlThe media access control data communication protocol sub-layer, also known as the medium access control, is a sublayer of the data link layer specified in the seven-layer OSI model , and in the four-layer TCP/IP model...