Error detection/correction and fault detection/recovery – Pulse or data error handling – Error count or rate
Reexamination Certificate
2000-04-24
2004-12-28
Lamarre, Guy J. (Department: 2133)
Error detection/correction and fault detection/recovery
Pulse or data error handling
Error count or rate
C714S758000
Reexamination Certificate
active
06836862
ABSTRACT:
TECHNICAL FIELD
The present invention relates to systems and devices connected using wireless links, specifically systems and devices that use the Bluetooth technology. In particular, the present invention pertains to measurement of the data transfer integrity (e.g., the bit error rate) of a wireless connection.
BACKGROUND ART
Computer systems and other types of consumer electronic devices are commonly linked to each other and to peripheral devices using a myriad of different types of cables and connectors. As these devices grow in number and variety, their cables and connectors can often become quite cumbersome to work with. Accordingly, efforts are underway to develop technologies allowing hardware connections to be replaced with wireless ones.
One such technology is the Bluetooth technology. Bluetooth is the code name for a technology specification for small form factor, low-cost, short-range radio links between personal computers (PCs), mobile phones and other devices. Bluetooth is targeted at mobile and business users who need to establish a link, or small network, between their computer, cellular phone and other peripherals. The required and nominal range of Bluetooth is thus set to approximately ten (10) meters. To support other uses, for example the home environment, Bluetooth can be augmented to extend the range to up to 100 meters.
The Bluetooth technology will allow the many proprietary cables that connect one device to another to be replaced with short-range radio links. The Bluetooth technology is based on a high-performance, yet low-cost, integrated radio transceiver. For instance, Bluetooth transceivers built into both a cellular telephone and a laptop computer system would replace the cables used today to connect a laptop to a cellular telephone. Printers, personal digital assistants (PDAs), desktops, fax machines, keyboards, joysticks and virtually any other digital device can be part of a Bluetooth system. Bluetooth radio technology can also provide: a universal bridge to existing data networks, a peripheral interface, and a mechanism to form small private ad hoc groupings (“scatternets” or “piconets”) of connected devices away from fixed network infrastructures.
Bluetooth is being designed to operate in a noisy radio frequency environment. A Bluetooth radio uses a fast acknowledgment and frequency-hopping scheme to make the link robust. Bluetooth radio modules avoid interference from other signals by hopping to a new frequency after transmitting or receiving a packet. Compared with other systems operating in the same frequency band, the Bluetooth radio typically hops faster and uses shorter packets. Short packets and fast hopping limit the impact of domestic and professional microwave ovens, for example. Use of Forward Error Correction (FEC), with encoding optimized for an uncoordinated environment, limits the impact of random noise on long-distance links. The Bluetooth radio is therefore typically more robust than other systems.
Robustness is especially significant in instances where the packets are being used for data transmission, as opposed to voice applications. In a voice application, such as a conversation over a cell phone connection, the intended message can still be delivered if some of the packets are missing or if there is some interference or noise present. However, with data transmission, such as between a peripheral data storage device and a computer system, each data packet is important and cannot be lost.
Hence, the Bluetooth specification provides mechanisms for determining whether a data packet is successfully received, so that data packets that are lost or that contain errors introduced during transmission can be retransmitted until they are successfully received. For example, according to the Bluetooth specification, the receiving device sends an acknowledgment signal for each data packet to the transmitting device to indicate whether or not the data packet was successfully received. The transmitting device retransmits the data packet if no acknowledgment signal is sent, or if the acknowledgment signal indicates that the data packet was received but contained an error.
Devices used for voice applications, such as cell phones, are generally equipped with a Receiver Signal Strength Indicator (RSSI) that can be used to measure the strength of the incoming signal. The Bluetooth specification also provides for an optional RSSI for measuring the receiver signal strength. However, signal strength indication does not provide an adequate measure of data transfer integrity or reliability; that is, signal strength does not necessarily have a direct bearing on whether all data packets will be successfully received. For example, the receiving device may be getting a strong signal, but the signal may only contain noise, or perhaps the receiving or transmitting device has a fault that introduces errors into the data packets. Thus, even though the RSSI may indicate that the signal is strong, data packets may still be lost or received with errors. As a result, even with a strong signal, it may be necessary to retransmit data packets over and over until they are successfully received. Thus, while the RSSI described by the Bluetooth specification may be relevant for voice applications, it is not adequate for data transmission.
Clearly, it is not desirable to repeatedly retransmit data packets. The resources of both the receiving and transmitting devices are lied up sending and receiving the data packets, verifying whether they were accurately received (e.g., decoding, cyclic redundancy checking, etc.), and sending and receiving acknowledgment signals. Each time the data packet is retransmitted, the amount of effort associated with handling and processing the data packet must be duplicated.
Accordingly, a need exists for a device and/or method that can be used to measure the integrity of a wireless connection for data transmission. A need also exists for a device and/or method that can satisfy the above need and that can provide the measurement information to a user. In particular, a need exists for a system and/or method that can satisfy the above needs for Bluetooth-enabled devices.
DISCLOSURE OF THE INVENTION
The present invention provides a device and method that can be used to measure the integrity of a wireless connection for data transmission and to provide the measurement information to a user. In particular, the present invention provides a device and method that satisfies the above needs for Bluetooth-enabled devices.
In the present embodiment, the present invention pertains to a device and method for monitoring the data transfer integrity of a wireless connection between two devices, such as two Bluetooth-enabled transceivers. A number of data packets are transmitted from one of the two devices to the other in a first-occurring transmission. The receiving device indicates to the transmitting device whether any of the data packets were not successfully received. Any data packets that were not successfully received are retransmitted. The data transfer integrity of the wireless connection is measured, for example, by determining the number of data packets successfully transmitted in the first-occurring transmission relative to the total number of data packets transmitted and retransmitted. The measurement information can be provided to a user or to another device. Embodiments of the present invention can be implemented using either the receiving device or the transmitting device.
In one embodiment, acknowledgment signals are sent by the receiving device to the transmitting device to indicate whether or not the data packets were successfully received. In this embodiment, the acknowledgment signals associated with the data packets successfully transmitted in a first transmission can be counted, and the acknowledgment signals associated with any retransmitted data packets can also be counted. The measure of data packet transfer integrity can be determined using these counts.
In another embodiment, a data packet transmitted in a first transmission and
Erekson Rich
Goff Darrell
3Com Corporation
Lamarre Guy J.
Trimmings John
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