Telecommunications – Receiver or analog modulated signal frequency converter – Measuring or testing of receiver
Reexamination Certificate
2002-04-10
2004-12-28
Vuong, Quochien B. (Department: 2685)
Telecommunications
Receiver or analog modulated signal frequency converter
Measuring or testing of receiver
C455S234100, C455S245100, C375S345000
Reexamination Certificate
active
06836647
ABSTRACT:
The present invention relates generally to wireless telecommunication systems, and more specifically to reliably estimating the power of a signal received in a receiver operating according to a CDMA (or similar) standard, even if the signal includes a significant amount of interference. The present invention is especially useful when the receiver uses the economically advantageous direct-conversion architecture because the direct-conversion open-loop power control circuit filters out less interference when compared to a standard super-heterodyne receiver.
BACKGROUND OF THE INVENTION
Wireless telecommunication technology has revolutionized the way people communicate over a distance. From the inception of modern telecommunication systems in the nineteenth century, virtually all such systems, save those relying on line-of-sight, are operated over a wire. Using a pattern of electrical signals transmitted from one end of the wire to the other, devices at each end have been able to establish effective and reliable communications. More accurately, to traverse long distances the electrical signals traveled a number of wires interconnected by switches to form a network. The switches permit almost any desired combination of wires to be connected so that any device may connect and communicate with any other, so long as they are both linked to the network and not otherwise occupied. This type of network, which started as telegraph and became telephone, is now often referred to as the plain-old telephone system (POTS). Similar private or limited-access networks are also in current use. Such networks provide a reliable vehicle for communications traffic, including voice and data, between devices such as telephones and computers. The main disadvantage of the POTS and similar wire line systems is that these devices must be located at a network-access point to which they are physically connected, and cannot be relocated during an ongoing communication session. In addition, whatever network resources are employed to establish the continuous connection between the calling party and the called party must remain so employed for the duration of the session-even at intervals where no actual communication is taking place.
Wireless communications, which rely chiefly on radio waves, address both of these concerns. Although the first radio transmission took place years ago, it is only in the relatively recent past that the technology has progressed to allow widespread use of wireless communication by the general population. A great many people now subscribe to mobile as well as (or instead of) wireline service. Typically, subscribers will have one or more mobile stations capable of radio communication with network transceivers located through the network coverage area. The mobile station itself includes a transmitter and a receiver, and will usually be a telephone, computer, personal digital assistant (PDA), or similar device. Naturally, there is no requirement that the mobile station actually be movable, and as used herein the term “mobile station” will apply to these devices and any others similarly capable of radio communication with a wireless network.
FIG. 1
is a block diagram illustrating selected components of a typical wireless network
100
, as might be used in communicating with mobile stations practicing received-power estimation according to the present invention. The network
100
includes a plurality of base service stations (BSSs), here BSS
105
, BSS
110
, and BSS
115
. Although only three BSSs are shown, however, in an actual network there would be a great many. Each BSS includes a base station transceiver (BST) and a base station controller (BSC). In
FIG. 1
, for example, BST
106
and BSC
107
are included in BSS
105
; BST
111
and BSC
112
in BSS
110
; and BST
116
and BSC
117
in BSS
115
. Alternately, a single BSC may control a number of BSTs. The coverage area of network
100
is divided into a number of cells, each having a BST (and perhaps a BSC). For purposes of illustration, three cells are enumerated in
FIG. 1
as cell
104
, cell
109
, and cell
114
. A typical network has many such cells that, unlike these illustrated in
FIG. 1
, may vary in size and overlap each other.
Individual subscribers use mobile stations, such as mobile station (MS)
130
, to communicate with and through the network, usually through the BST covering the cell in which the mobile station is currently located, or the BST of a neighboring cell. In this way each radio frequency being used for mobile station to base station communication may be re-used for similar communications in another cell, so long as the other cell is sufficiently far away to prevent the signals from crossing or interfering with one another. Naturally, transmission power is limited so that transmissions taking place in one cell do not reach (at significant levels) another cell where the same frequency is being used. In the embodiment of
FIG. 1
, MS
130
is in communication with BSS
115
through a radio-frequency (RF) link
135
. RF link
135
includes a forward link
136
, which carries transmissions from BST
116
to MS
130
, and a reverse link
137
, which the MS
130
uses for transmitting to BST
116
. Reverse link
137
may be used for both traffic (actual communication) and control signaling. The same is true of forward link
136
, which includes a pilot channel, a sync channel, and a paging channel. A pilot channel signal is transmitted continuously by each BST and is the means by which a mobile station locates a base station so that it can register (makes its presence known to the network) or establish a voice or data link for actual communication. The sync-channel message allows each mobile station to obtain frame synchronization of the CDMA signal. The paging channel is used for paging mobile stations to provide notice of incoming calls, and for similar messages.
Under ordinary conditions, MS
130
communicates only with BSS
115
while located in cell
114
. As it travels toward, for example, cell
109
, it detects that the pilot channel message from BSS
110
is getting stronger, and may establish communication with it as well. (The network may also allow for communication through the BSSs associated with neighboring cells where the closest BSS is available.) This redundancy enables continuity of communication as MS
130
relocates. When a mobile station travels from one cell to another, it switches from one BST to another in a process called “hand off.” Ideally, communications with the second BST will be established before the link to the original BST is broken, in which case (called “soft hand-off”) the subscriber will perceive little or no break in the transmission.
BSSs may communicate directly with one another, such as BSS
105
and BSS
110
of
FIG. 1
, although they are all connected directly or indirectly through a mobile switching center (MSC) such as MSC
120
. MSC
120
switches voice calls between mobile stations communicating with BSSs it is connected to, and switches calls to any other devices through the network (not shown) itself. Information concerning the mobile stations operating in the area is stored in a Visitor Location Register (VLR) database
122
, which is connected to the MSC
120
. MSC
120
may also include a packet-data switching node (PDSN)
124
that similarly switches packet data to and from more modern mobile stations.
As mentioned above, cellular telephony's frequency re-use allows many more subscribers to be actively communicating than would otherwise be possible. That is, if all of the mobile stations in, for example, were each allocated their own frequency to use anywhere in a large metropolitan area, the available channels would soon be exhausted and busy signals would be very common. With frequency re-use, however, the same frequency channel being used by one mobile station may be assigned to another operating only a few miles away.
In addition, several multiple access schemes have been developed. Standard frequency-division multiple access (FDMA) simply di
Carbone Nick
Rimini Roberto
Le Nhan
Nokia Corporation
Vuong Quochien B.
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