Telecommunications – Transmitter and receiver at same station – Radiotelephone equipment detail
Reexamination Certificate
1998-08-14
2002-10-08
Urban, Edward F. (Department: 2685)
Telecommunications
Transmitter and receiver at same station
Radiotelephone equipment detail
C455S343200, C455S575100, C455S067150, C455S067700, C455S422100, C455S424000
Reexamination Certificate
active
06463307
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to communication networks having mobile wireless terminals. In particular, the present invention relates to management of power consumption of mobile wireless terminals having an active communication connection.
BACKGROUND OF THE INVENTION
In a public asynchronous transfer mode (ATM) network, charging of unspecified bit rate (UBR) connections and perhaps also available bit rate (ABR) connections will most likely either be based on the traffic volume of the connections or on a fixed subscription fee, instead of the traditional charging based on time duration of a session or connection. Volume based charging as well as a fixed subscription fee arrangement provide incentives for users to change their usage behavior. For example, instead of placing short and concise phone calls, users may keep telecommunication connections established for long periods of time, while sending and receiving data infrequently so that the average bandwidth utilization is low. Many new types of applications may arise, that allow users to explore the feature of having constant connectivity, i.e., a continuous connection, that is free where the users pay only when data is transferred across the connection. For such connections, when the users have low average usages long periods of time can elapse between consecutive data packet transmissions.
A private ATM network can also provide users with the option of keeping connections to various servers established for long periods of time. After the initial connection is established, a user can have constant connectivity to a file server, mail server, etc. A mail tool can then poll the POP account on behalf of the user at intervals such as 10-15 minutes, without any need to re-establish a connection each time. Thus, where communication is via modem, repetition of the dial-up process can be avoided. Similarly, a user's word processor can auto-save current document versions at regular intervals (e.g., every 10 minutes) on the file server without having to re-establish a connection each time. In such situations ATM connections can remain established for long periods of time, even when the average usage of such connections is very low.
Since TCP/IP provides a connection-less transport service, most local area network (LAN) applications take the connectivity to various servers for granted without any preceding dial-up service. To offer LAN applications and ATM applications the same transport service in a wireless LAN (WLAN) or a wireless ATM (WATM) network, a mobile terminal in the network should keep its communication connection(s) established for long periods of time. However, this tends to increase power consumption of the mobile terminal, which may have a finite and thus time-limited power supply such as a battery. Accordingly, it is important to ensure that the mobile terminal saves power whenever it has no data to receive or transmit.
FIG. 1
shows an exemplary system with a base station (BS) and multiple mobile terminals (MT)
102
-
112
.
Conventional cellular mobile systems normally support some mechanisms or procedures that enable the mobile terminal to save some battery power. For example, a paging mechanism enables the mobile terminal to enter a power-saving mode while it is inactive, i.e., when it has no communication connection established. An “inactive” mobile terminal regularly listens to a paging channel at specified time intervals, but in between times it turns off its receiver ands sleeps or hibernates.
Paging in a WLAN or WATM system can be sent on a fixed frame basis, or on a superframe basis where the superframe contains multiple frames. In the beginning of each superframe, the BS has the opportunity to page one or several mobile terminals. The mobile terminals can be divided into paging groups in order to enable them to sleep or hibernate for a longer time than the duration of a superframe. As shown in
FIG. 2
, an exemplary downlink channel (DLC) frame structure has a superframe
200
which conveys paging messages in its header
202
. Within the body of the superframe
200
are individual frames such as medium access control (MAC) frames
204
, each of which can have a broadcast field
206
that provides information about the contents of the individual frame
204
. The MAC protocol is described in greater detail in copending application Ser. No. 09/046,652, which is hereby incorporated by reference. A hibernating terminal may wake up for every nth superframe to check for a paging message. Where multiple mobile terminals are organized into groups, the mobile terminals in each group can be organized to wake up for the same superframe, and different groups wake up for different superframes. The DLC frame structure allows mobile terminals to sleep for short periods of time during transmission of certain parts of the frame, so that an active terminal will only have to stay awake to receive the various headers and broadcast fields of the DLC frames, as well as to receive packets directed to the active terminal and transmit packets.
Although conventional cellular mobile systems can provide a paging mechanism as described above to save battery power in inactive mobile terminals, and although there are methods available to enable active terminals to sleep for short intervals, (for example during parts of a superframe), these solutions lack methods to enable active terminals with established connections to sleep or hibernate for long periods of time.
In the IEEE 802.11 specification (which is hereby incorporated by reference) there is a power saving procedure for active terminals (i.e., terminals with established connections). Whenever a terminal decides to enter or exit the power saving mode, it informs the BS. When the terminal is in the power saving mode, the BS buffers all incoming packets designating the terminal. If the buffer in the BS overflows, the excess packets are discarded. The maximum duration of the power saving (or sleeping/hibernating) mode is determined by the terminal itself.
In a “Magic Wand” specification (which is hereby incorporated by reference), there is a power saving procedure for terminals with established connections. The terminal itself decides when and for how long it will sleep or hibernate. The terminal can determine the sleep duration based on the quality of service (QOS) of its established connections. Whenever a terminal enters a power saving mode in which it sleeps, it informs the BS about the duration of the sleep.
Both the IEEE 802.11 specification and the Magic Wand specification allow an active terminal to enter a power saving mode. When the terminal is in the power saving mode, the BS buffers packets designated for the terminal until the terminal exits the power saving mode. Thus, an optimum sleep duration time for the terminal depends to some extent on the buffering capacity of the BS. Since the BS knows its buffering capacity but the terminal decides the sleep duration time instead of the BS, the terminal sleep duration time is likely to be sub-optimal.
Furthermore, the power saving methods of the IEEE 802.11 and the Magic Wand specifications each require that a terminal send a message to the BS every sleeping period. For example, in accordance with the Magic Wand specification, the terminal indicates to the BS that it will sleep for “X” milliseconds. When the X millisecond time period expires, the terminal must awaken to check for any downlink packets to receive. In many cases the terminal will find that it had no packet to receive, and it will then decide to enter the power-saving sleep mode again. However, before the terminal can return to the power-saving mode it must inform the BS how long it will sleep. The transmission of the “sleep” message and the reception of a response from the BS will consume battery power.
SUMMARY OF THE INVENTION
In accordance with an embodiment of the invention, power consumption of a mobile terminal can be further reduced by providing a system wherein a hibernating mobile terminal remains hibernating in a hibernation sta
Larsson Mikael
Larsson Peter
Burns Doane Swecker & Mathis L.L.P.
Milord Marceau
Telefonaktiebolaget LM Ericsson
Urban Edward F.
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