WO2013152506A1

WO2013152506A1 - Reverse transmission in a wireless surveillance sensory data transmission network

Info

Publication number: WO2013152506A1
Application number: PCT/CN2012/074010
Authority: WO
Inventors: Shi Chen; Haifeng Wang; Jun Xia; Kai Yu; Zhiyong Bu; Guangyu Liu
Original assignee: Renesas Mobile Corporation
Priority date: 2012-04-13
Filing date: 2012-04-13
Publication date: 2013-10-17

Abstract

The invention allows reverse transmission in a local section of a wireless surveillance sensory data transmission network. A failure is detected in an interface gateway of a local section of a wireless surveillance sensory data transmission network. The local section comprises the interface gateway and a number of non-interface gateways arranged in a chain topology with the interface gateway being a destination for hop-by-hop transmission of wireless surveillance sensory data in the local section. In response to the detected failure, it is determined to initialize a reverse transmission of information related to the hop-by-hop transmission of wireless surveillance sensory data. The reverse transmission is to be performed hop-by-hop from the non-interface gateway in which the failure was detected to at least part of the remaining non-interface gateways in the local section.

Description

REVERSE TRANSMISSION IN A WIRELESS SURVEILLANCE SENSORY DATA TRANSMISSION NETWORK

BACKGROUND OF THE INVENTION:

Field of the Invention:

The invention relates to reverse transmission in a wireless surveillance sensory data transmission network.

Description of the Related Art:

Modernization of the electric power grid is central to efforts to increase energy efficiency, transition to renewable sources of energy, and reducing of greenhouse gas emission. The electrical power system is a large and complicated system. In order to maintain the security and stability of system, communication networks and information technology are beginning to be used in electrical power systems. This new type of hybrid network is a so-called smart grid. Information and communication technologies are merging with traditional energy delivery systems, and there is a need to deliver higher quality and more reliable power from the aging infrastructure while keeping the overall costs low.

Technically, the smart grid can be considered a self-healing power system based on information technology. Smart grid will combine novel control, information and management techniques, realize a series of intelligent interactive activities from power transmission to electricity end users, and optimize electricity generation, transmission and distribution scientifically and systematically. The application of advanced digital technologies (i.e., microprocessor- based measurement and control, communications, computing, and information systems) are expected to greatly improve the reliability, security, interoperability, and efficiency of the electric grid, while reducing environmental impacts.

In conventional electricity systems, power transmission depends mainly on high voltage electrical power transmission lines. This kind of transmission line may span e.g. a few kilometers, and huge amounts of electrical towers are employed for mounting the long transmission line. These towers are responsible for relaying the power transmission line as ordinary stents. Routine maintenance of electric transmission lines depends almost totally on human inspection. With restricted means of inspection, once breakdown happens in a certain section of a long transmission line, it is hard to precisely locate the failure point and troubleshoot promptly. Thus there is a need to develop new technology for ensuring power transmission security.

In a smart grid, wireless sensor network (WSN) may be employed for grid status surveillance, including monitoring physical parameters of electrical tower and transmission line status, such as soil regime, metal fatigue, wire firmness, etc. Sensors installed on the towers and electric wires send monitoring data periodically to the local gateway hop by hop. However, it is well-known that a WSN is an energy restricted network. That is, the transmission power of a sensor node is limited since the equipped battery is hard to replace or recharge in most cases.

Some towers on the surveillance line may be covered by cellular systems, and the gateways on these towers can report monitoring data e.g. to a local base station or eNB (evolved Node B) . Gateways in some towers on the surveillance line may be equipped with e.g. fiber interfaces connected to the Internet. These gateways act as the destinations of the nearby monitoring nodes. Herein, these gateways are called local destinations. Gateways located out of the coverage of cellular systems and without a fiber connection or a similar fixed connection, have to exchange monitoring data via multi-hop manner to their respective local destination. Herein, the section that is comprised of such gateways, is called an ad-hoc section or a local section .

Therefore, for the purpose of sensory data collection in an energy restricted scenario, one may consider some type of long range wireless technology for forwarding the sensory data from each tower. The devices installed on the towers may be so-called gate^¬ ways (or nodes or stations) equipped with both a WSN module and a long range wireless module. Transmission procedure between gateways may be of periodic type. Transmission line maintenance may be operated in routine fashion for real-time monitoring. The gateways forward the sensory data via multiple hops to the local destination.

Data transmissions in each ad-hoc sections are operated in time-division duplex (TDD) mode. During a surveillance initialization phase, each gateway in the ad-hoc section can be configured to select its correct transmission direction. When a gateway in the middle of an ad-hoc section with e.g. a fiber connection breaks down, it forces its associated gateway transmissions into a deadlock status. Each tower in the ad-hoc section works in a duty-cycle mode. That is, after an active transmission period, a tower switches into a sleep mode in order to save energy.

However, e.g. a natural disaster or human factors may occasionally cause the gateway to break down. Since the surveillance reporting link based on the gateways installed on the transmission towers is a one-way link, intermediate gateway breakdown will cause any alarm report to fail. If the gateway on an intermediate tower breaks down, the remaining communication link to the interface gateway will be lost. Ob- viously, any interface gateway crash will paralyze the whole reporting network and deteriorate network robustness .

As mentioned above, different from a mesh to^¬ pology network, an electric transmission line surveil^¬ lance network is of the fragile chain type topology. In this type of network, breakdown of any node will cause a network disconnection, which is hard to avoid in practical situations. Therefore, the transmission mechanism between the gateways needs to be adaptive in order to guarantee that the sensory data reaches its destination. Accordingly, transmission robustness is a major aspect of a power transmission line surveillance network .

Therefore, an object of the present invention is to alleviate the problems described above and to introduce a solution that allows reverse transmission in a local section of a wireless surveillance sensory data transmission network e.g. if a failure occurs in the local section.

SUMMARY OF THE INVENTION:

A first aspect of the present invention is a method in which, a failure in an interface gateway of a local section of a wireless surveillance sensory data transmission network is detected. The local section comprises the interface gateway and a number of non- interface gateways arranged in a chain topology with the interface gateway being a destination for hop-by- hop transmission of wireless surveillance sensory data in the local section. The interface gateway comprises a communication interface for communicating the wireless surveillance sensory data to an external data network. In response to the detected failure, it is determined to initialize a reverse transmission of information related to the hop-by-hop transmission of wireless surveillance sensory data. Here, the reverse transmission is to be performed hop-by-hop from the non-interface gateway in which the failure was de^¬ tected to at least part of the remaining non-interface gateways in the local section.

A second aspect of the present invention is an apparatus which comprises at least one processor, and at least one memory including computer program code. The at least one memory and the computer program code are configured to, with the at least one proces- sor, cause the apparatus at least to perform:

detecting a failure in an interface gateway of a local section of a wireless surveillance sensory data transmission network, the local section comprising the interface gateway and a number of non- interface gateways arranged in a chain topology with the interface gateway being a destination for hop-by- hop transmission of wireless surveillance sensory data in the local section, and the interface gateway comprising a communication interface for communicating the wireless surveillance sensory data to an external data network; and

in response to the detected failure, initializing a reverse transmission of information related to the hop-by-hop transmission of wireless surveillance sensory data, the reverse transmission to be performed hop-by-hop from the non-interface gateway in which the failure was detected to at least part of the remaining non-interface gateways in the local section.

A third aspect of the present invention is a computer program which comprises code adapted to cause the following when executed on a data-processing system :

detecting a failure in an interface gateway of a local section of a wireless surveillance sensory data transmission network, the local section compris^¬ ing the interface gateway and a number of non- interface gateways arranged in a chain topology with the interface gateway being a destination for hop-by- hop transmission of wireless surveillance sensory data in the local section, and the interface gateway com^¬ prising a communication interface for communicating the wireless surveillance sensory data to an external data network; and

in response to the detected failure, determining to initialize a reverse transmission of infor^¬ mation related to the hop-by-hop transmission of wire- less surveillance sensory data, the reverse transmis^¬ sion to be performed hop-by-hop from the non-interface gateway in which the failure was detected to at least part of the remaining non-interface gateways in the local section.

A fourth aspect of the present invention is an apparatus which comprises at least one processor means, and at least one memory means including computer program code means. The at least one memory means and the computer program code means are, with the at least one processor means, for causing the ap^¬ paratus at least to perform:

detecting a failure in an interface gateway of a local section of a wireless surveillance sensory data transmission network, the local section compris- ing the interface gateway and a number of non- interface gateways arranged in a chain topology with the interface gateway being a destination for hop-by- hop transmission of wireless surveillance sensory data in the local section, and the interface gateway com- prising a communication interface for communicating the wireless surveillance sensory data to an external data network; and

in response to the detected failure, initializing a reverse transmission of information related to the hop-by-hop transmission of wireless surveillance sensory data, the reverse transmission to be performed hop-by-hop from the non-interface gateway in which the failure was detected to at least part of the remaining non-inter ace gateways in the local section.

In an embodiment of the invention, the transmissions are of time-division multiplexing type. In this embodiment, a time slot is calculated in a non- interface gateway for listening for the reverse transmission according to IS = 2xSI - CS, wherein IS is the time slot for listening, SI is the number of the non- interface gateways in the local section involved in the reverse transmission, and CS is a current time slot assigned to the non-interface gateway for the transmission of wireless surveillance sensory data in the local section.

In an embodiment of the invention, the trans- missions are of time-division multiplexing type. In this embodiment, a time slot is calculated in a non- interface gateway for listening for the reverse transmission according to at least one of IS = [ (2xSI - CS - 1) mod superframe] + 1 and IS = [ (2xSI - CS) mod su- perframe] + 1, wherein IS is the time slot for listening, SI is the number of the non-interface gateways in the local section involved in the reverse transmission, CS is a current time slot assigned to the non- interface gateway for the transmission of wireless surveillance sensory data in the local section, and superframe is the total number of time slots in one duty cycle of the non-interface gateway. In case the superframe is an even number, and the difference be^¬ tween the assigned CS and the calculated IS is one of 2 and 0, in this embodiment, it is determined to delay forwarding a received reverse transmission for one time slot in the non-interface gateway.

In an embodiment of the invention, the transmissions are of time-division multiplexing type. In this embodiment, a time slot is calculated in a non- interface gateway for listening for the reverse transmission according to at least one of IS = [ (2xSI - CS ~ 1) mod superframe] + 1 and IS = [ (2xSI - CS) mod su- perframe] + 2 , wherein IS is the time slot for listening, SI is the number of the non-interface gateways in the local section involved in the reverse transmission, CS is a current time slot assigned to the non- interface gateway for the transmission of wireless surveillance sensory data in the local section, and superframe is the total number of time slots in one duty cycle of the non-interface gateway. In case the superframe is an odd number, and the difference between the assigned CS and the calculated IS is 3, in this embodiment, it is determined to delay forwarding a received reverse transmission for two time slots in the non-interface gateway.

In an embodiment of the invention, SI is stored in the non-interface gate-ways.

In an embodiment of the invention, the information related to the hop-by-hop transmission of wireless surveillance sensory data comprises at least one of the wireless surveillance sensory data and an alarm about the detected failure.

In an embodiment of the invention, the surveillance sensory data relates to one of a ^ electrical power transmission line and a traffic line.

In an embodiment of the invention, the computer program of the third aspect is stored on a computer readable medium.

It is to be understood that the aspects and embodiments of the invention described above may be used in any combination with each other. Several of the aspects and embodiments may be combined together to form a further embodiment of the invention. A method, an apparatus, or a computer program which is an aspect of the invention may comprise at least one of the embodiments of the invention described above.

The invention allows reverse transmission in a local section of a wireless surveillance sensory da- ta transmission network e.g. if a failure occurs in the local section. Accordingly, a transmission line can achieve a self-healing function. Furthermore, transmission delay caused by the failure of the interface gateway acting as a local destination is greatly improved. Furthermore, the dead-lock problem described above is avoided.

BRIEF DESCRIPTION OF THE DRAWINGS:

The accompanying drawings, which are included to provide a further understanding of the invention and constitute a part of this specification, illustrate embodiments of the invention and together with the description help to explain the principles of the invention. In the drawings:

Fig. 1 is a block diagram illustrating an apparatus according to an embodiment of the invention; and

Figs . 2a-2c describe methods according to em^¬ bodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION:

Reference will now be made in detail to the embodiments of the present invention, examples of which are illustrated in the accompanying drawings.

In the examples of Figures l-2c, surveillance sensory data is associated with a smart power grid, and the gateways are comprised in electrical power transmission towers. However, it is to be understood that the invention is not limited to this. For example, surveillance sensory data may be associated with traf^¬ fic line surveillance, such as e.g. railway surveillance .

Figure 1 is a block diagram illustrating an apparatus 130 according to an embodiment of the invention. As shown in Figure 1, the apparatus 130 may be implemented in a gateway 120 which in turn may be located e.g. in an electrical transmission tower 100. In the embodiment of Figure 1, the electrical transmis^¬ sion tower 100 further comprises sensors 110i, 110₂ and IIO3 which are configured to monitor e.g. physical pa^¬ rameters of the electrical transmission tower 100 and transmission line status, such as soil regime, metal fatigue, wire firmness, etc. The monitored surveil^¬ lance sensory data is collected by the gateway 120, and then e.g. forwarded to a subsequent gateway in a subsequent electrical transmission tower of a smart power grid. Alternatively, if the gateway in question is a an interface gateway, i.e. a gateway comprising a communication interface (not illustrated in Figure 1) for communicating the collected surveillance sensory data to an external data network, the gateway in ques^¬ tion may forward the collected surveillance sensory data to the external data network.

The apparatus 130 comprises at least one processor 131, and at least one memory 132 including computer program code 133. The at least one memory 132 and the computer program code 133 are configured to, with the at least one processor 131, cause the apparatus 130 at least to perform:

The information related to the hop-by-hop transmission of wireless surveillance sensory data may comprises the wireless surveillance sensory data and/or an alarm about the detected failure.

In an embodiment of the invention further illustrated in connection with Figure 2a, the transmissions are of time-division multiplexing type, and the at least one memory 132 and the computer program code 133 may be further configured to, with the at least one processor 131, cause the apparatus 130 to further perform:

calculating, in a non-interf ce gateway, a time slot for listening for the reverse transmission according to IS = 2xSI - CS, wherein IS is the time slot for listening, SI (or section indicator) is the number of the non-interface gateways in the local section involved in the reverse transmission, and CS is a current time slot assigned to the non-interface gateway for the transmission of wireless surveillance sensory data in the local section.

In another embodiment of the invention further illustrated in connection with Figure 2b, the transmissions are of time-division multiplexing type, and the at least one memory 132 and the computer program code 133 may be further configured to, with the at least one processor 131, cause the apparatus 130 to further perform:

calculating, in a non-interface gateway, a time slot for listening for the reverse transmission according to at least one of IS = [ (2xSI - CS - 1) mod superframe] + 1 and IS = [ (2xSI - CS) mod superframe] + 1, wherein IS is the time slot for listening, SI is the number of the non-interface gateways in the local section involved in the reverse transmission, CS is a current time slot assigned to the non-interface gateway for the transmission of wireless surveillance sen- sory data in the local section, and superframe is the total number of time slots in one duty cycle of the non-interface gateway.

In this embodiment, when the superframe is an even number, the difference between the assigned CS and the calculated IS is one of 2 and 0, the at least one memory 132 and the computer program code 133 may be further configured to, with the at least one processor 131, cause the apparatus 130 to further perform:

determining to delay forwarding a received reverse transmission for one time slot in the non- interface gateway.

In yet another embodiment of the invention further illustrated in connection with Figure 2c, the transmissions are of time-division multiplexing type, and the at least one memory 132 and the computer program code 133 may be further configured to, with the at least one processor 131, cause the apparatus 130 to further perform:

calculating, in a non-interface gateway, a time slot for listening for the reverse transmission according to at least one of IS = [ (2xSI ~ CS - 1} mod superframe] + 1 and IS = [ (2xSI ~ CS) mod superframe] + 2, wherein IS is the time slot for listening, SI is the number of the non-interface gateways in the local section involved in the reverse transmission, CS is a current time slot assigned to the non-interface gateway for the transmission of wireless surveillance sensory data in the local section, and superframe is the total number of time slots in one duty cycle of the non-interface gateway.

In this embodiment, when the superframe is an odd number, the difference between the assigned CS and the calculated IS is 3, the at least one memory 132 and the computer program code 133 may be further configured to, with the at least one processor 131, cause the apparatus 130 to further perform:

determining to delay forwarding a received reverse transmission for two time slots in the non- interface gateway.

In all of the above embodiments SI may be stored in the non-interface gateways, e.g. by caching.

Next, embodiments of methods of the invention will be described with reference to Figures 2a-2c.

The arrangement in Figure 2a includes electrical power transmission towers I O O 10-IOO14. The solid lines connecting the electrical power transmission towers I O O 10-IOO14 denote electrical power transmission lines. The details of the electrical power transmission towers I O O 10-IOO14 are similar to the electrical power transmission tower 100 of Figure 1, i.e. each of them includes at least the apparatus 130 of the inven- tion and the gateway 120, even though they are not explicitly shown in Figure 2a for the sake of clarity. In the embodiment of Figure 2a, the electrical power transmission towers I O O 10-IOO13 comprise non-interface gateways, and the electrical power transmission tower IOO14 comprises an interface gateway. A local section comprises the interface gateway (in tower IOO14) and a number of non-interface gateways (in towers 100io^_100i₃) arranged in a chain topology with the interface gateway {in tower IOO14) being a destination for hop-by-hop transmission (normal transmission) of wireless surveillance sensory data in the local section. The interface gateway (in tower 100₁₄) comprises a communication interface for communicating the wireless surveillance sensory data to an external data network (not shown in Figure 2a) .

In the embodiments of Figures 2a-2c, during the wireless surveillance sensory data exchange phase, each gateway 120 communicates in a time-division multiplexing (TDM) wireless communication mode. In such a case, data exchange processes may be restricted to a time slot that is predefined in the network initial!- zation stage. Each gateway 120 may switch its own sta^¬ tus according to conditions of its adjacent gateways. During periodic transmission maintenance, sensory data is collected by the nearby gateways and transmitted to the interface gateway in a multi-hop fashion according to a pre-defined transmission timetable.

In the embodiment of Figure 2a, timeslots Tl- T4 shown above the electrical power transmission towers I O O 10-IOO14 are allocated for normal transmission, and timeslots T5-T7 shown below the electrical power transmission towers lOGio-lOOn are allocated for the reverse transmission procedure of the invention. For example, timeslot Tl is the timeslot during which the gateway 120 in the electrical power transmission tower lOOio transmits in normal transmission, timeslot T2 Is the timeslot during which the gateway 120 in the electrical power transmission tower 100n transmits In normal transmission, etc.

At step 201, a failure in an interface gateway (In tower 100₁₄) of the local section of the wire- less surveillance sensory data transmission network is detected. The detection may be performed in the non- interface gateway (in tower IOO13) adjacent to the failed interface gateway (in tower 100i₄) . In response to the detected failure, it is determined in this in- terface gateway (in tower IOO₁₃) to initialize a reverse transmission of information related to the hop- by-hop transmission of wireless surveillance sensory data, step 202. The reverse transmission will be performed hop-by-hop from the non-interface gateway (in tower 100χ₃) in which the failure was detected to at least part of the remaining non-interf ce gateways (in towers I O O 10 - I O O 12 ) in the local section. In all the embodiments of the invention, for each gateway the total data transmission time is defined as an active period. Since each gateway has to switch into sleep mode to save energy, a sleep period is also defined. A superframe is the total number of time slots in one duty cycle of a gateway. In the embodiment of Figure 2a, 2 x active period < superframe, i.e. the gateways spend more time in sleep period than in active period. Accordingly, the reverse transmis- sion procedure can be operated in the non-active period of the superframe.

At step 203, respective time slots are calculated in each non-interface gateway (in towers 100io~ 100i₃) for listening for the reverse transmission. The calculation is performed according to IS = 2xSI - CS, wherein I S is the time slot for listening for the reverse transmission, S I is the number of the non- interface gateways in the local section involved in the reverse transmission, and CS is a current time slot assigned to the non-interface gateway for the transmission of wireless surveillance sensory data in the local section.

In the embodiment of Figure 2a, superframe consists of 9 timeslots, active period consists of 3 timeslots, and SI consists of 4 non-interface gateways (in towers I O O 1₀-IOO₁₃) . Accordingly, the listening time slot IS for the non-interface gateway in tower I O O 12 is 2x4-3=5. That is, as shown in Figure 2a, the current or normal time slot assigned to the non- interface gateway in tower I O O 12 is T3, and its time slot for listening for the reverse transmission is T5. Similarly, the listening time slot IS for the non- interface gateway in tower 100 is 2x4-2=6. That is, as shown in Figure 2a, the current or normal time slot assigned to the non-interface gateway in tower 100n is T2, and its time slot for listening for the reverse transmission is T6. The arrangement in Figure 2b includes electrical power transmission towers 10θ₂ο^_10θ2₉· The solid lines connecting the electrical power transmission towers IOO20-IOO29 denote electrical power transmission lines. The details of the electrical power transmission towers IOO20-IOO29 are similar to the electrical power transmission tower 100 of Figure 1, i.e. each of them includes at least the apparatus 130 of the invention and the gateway 120, even though they are not ex- plicitly shown in Figure 2b for the sake of clarity. In the embodiment of Figure 2b, the electrical power transmission towers IOO20-IOO28 comprise non-interface gateways, and the electrical power transmission tower IOO29 comprises an interface gateway. A local section comprises the interface gateway (in tower IOO₂₉) and a number of non-interface gateways (in towers 100₂o-100₂8) arranged in a chain topology with the interface gateway (in tower IOO29) being a destination for hop-by-hop transmission (normal transmission) of wireless sur- veillance sensory data in the local section. The interface gateway (in tower 100₂₉} comprises a communication interface for communicating the wireless surveillance sensory data to an external data network (not shown in Figure 2b) .

In the embodiment of Figure 2b, timeslots Tl-

T9 shown above the electrical power transmission towers 100₂o-100₂9 are allocated for normal transmission, and timeslots T10, T1-T3, T5-T8 shown below the electrical power transmission towers IOO2Q-IOO29 are allo- cated for the reverse transmission procedure of the invention. For example, timeslot Tl is the timeslot during which the gateway 120 in the electrical power transmission tower IOO20 transmits in normal transmission, timeslot T2 is the timeslot during which the gateway 120 in the electrical power transmission tower IOO21 transmits in normal transmission, etc. In the embodiment of Figure 2b, steps 201 and 202 are similar to those in the embodiment of Figure 2a, so they are not described again here.

In the embodiment of Figure 2b, active period < superframe < 2 x active period, i.e. the gateways spend more time to transmit data than in sleep period. Therefore, the reverse transmission procedure can be partially operated in the non-active period of the su^¬ per-frame. A collision avoidance mechanism needs to be implemented in the reverse transmission period.

At step 204, respective time slots are calculated in each non-interface gateway (in towers IOO20- 100₂e) f°^r listening for the reverse transmission. The calculation is performed according to at least one of IS = [ (2xSI - CS - 1) mod superframe] + 1 and IS = [ (2xSI - CS) mod superframe] + 1, wherein IS is the time slot for listening, SI is the number of the non- interface gateways in the local section involved in the reverse transmission, CS is a current time slot assigned to the non-interface gateway for the transmission of wireless surveillance sensory data in the local section, and superframe is the total number of time slots in one duty cycle of the non-interface gateway. However, if a gateway receive reverse signal- ing in the first time slot IS = [ (2xSI - CS - 1) mod superframe] + 1, it does not need to keep listening for reverse signaling at the next time slot IS = [ (2xSI - CS) mod superframe] + 1.

In the embodiment of Figure 2b, superframe consists of 10 timeslots, active period consists of 8 timeslots, and SI consists of 9 non-interface gateways {in towers IOO20-IOO2₈) . Accordingly, the listening time slot IS for the non-interface gateway in tower IOO25 s [(2x9-6-1) mod 10] + 1 = 2. That is, as shown in Figure 2b, the current or normal time slot assigned to the non-interface gateway in tower 100₂5 is T6, and its time slot for listening for the reverse transmis- sion is T2. Similarly, the listening time slot IS for the non-interface gateway in tower 100₂6 is [(2x9-7-1) mod 10] + 1 = 1. That is, as shown in Figure 2b, the current or normal time slot assigned to the non- interface gateway in tower IOO26 is T7, and its time slot for listening for the reverse transmission is Tl.

In the embodiment of Figure 2b, the super- frame is an even number (10) . In a gateway in which the difference between the assigned CS and the calcu- lated IS is one of 2 and 0, it is determined to delay forwarding a received reverse transmission for one time slot, step 205. More specifically, in the embodiment of Figure 2b, this applies to the gateway in the tower IOO24, for which the assigned CS is T5, and the calculated IS is T3, i.e. the difference between the assigned CS and the calculated IS is 5-3=2. As shown in Figure 2b, the gateway in the tower 100₂4 delays forwarding its received reverse transmission for one time slot, i.e. to time slot T5 instead of time slot T .

The arrangement in Figure 2c includes elec^¬ trical power transmission towers IOO30-IOO39. The solid lines connecting the electrical power transmission towers IOO30-IOO39 denote electrical power transmission lines. The details of the electrical power transmis^¬ sion towers IOO30-IOO39 are similar to the electrical power transmission tower 100 of Figure 1, i.e. each of them includes at least the apparatus 130 of the invention and the gateway 120, even though they are not ex- plicitly shown in Figure 2b for the sake of clarity. In the embodiment of Figure 2b, the electrical power transmission towers 100₃₀-100₃₈ comprise non-interface gateways, and the electrical power transmission tower IOO39 comprises an interface gateway. A local section comprises the interface gateway (in tower IOO₃9) and a number of non-interface gateways (in towers IOO₃₀-IOO38) arranged in a chain topology with the interface gate- way (in tower IOO₃₉) being a destination for hop-by-hop transmission (normal transmission) of wireless surveillance sensory data in the local section. The interface gateway (in tower 100₃₉) comprises a communica- tion interface for communicating the wireless surveillance sensory data to an external data network (not shown in Figure 2c) .

In the embodiment of Figure 2c, timeslots Tl- T9 shown above the electrical power transmission tow- ers IOO3Q-IOO39 are allocated for normal transmission, and timeslots T10-T11, T1-T2, T5-T8 shown below the electrical power transmission towers IOO30-IOO39 are allocated for the reverse transmission procedure of the invention. For example, timeslot Tl is the time- slot during which the gateway 120 in the electrical power transmission tower IOO30 transmits in normal transmission, timeslot T2 is the timeslot during which the gateway 120 in the electrical power transmission tower IOO31 transmits in normal transmission, etc.

In the embodiment of Figure 2c, steps 201 and

202 are similar to those in the embodiment of Figure 2a, so they are not described again here.

In the embodiment of Figure 2c, active period < superframe < 2 x active period, i.e. the gateways spend more time to transmit data than in sleep period. Therefore, the reverse transmission procedure can be partially operated in the non-active period of the super-frame. A collision avoidance mechanism needs to be implemented in the reverse transmission period.

At step 206, respective time slots are calculated in each non-interface gateway (in towers IOO30- 100_3g) for listening for the reverse transmission. The calculation is performed according to at least one of IS = [(2xSl - CS - 1) mod superframe] + 1 and IS = [ (2xSI ~ CS) mod superframe] + 2, wherein IS is the time slot for listening, SI is the number of the non- interface gateways in the local section involved in the reverse transmission, CS is a current time slot assigned to the non-interface gateway for the transmission of wireless surveillance sensory data in the local section, and superframe is the total number of time slots in one duty cycle of the non-interface gateway. However, if a gateway receive reverse signaling in the first time slot IS = [ (2xSI - CS - 1) mod superframe] + 1, it does not need to keep listening for reverse signaling at the next time slot IS = [ (2xSI - CS) mod superframe] + 2.

In the embodiment of Figure 2c, superframe consists of 11 timeslots, active period consists of 8 timeslots, and SI consists of 9 non-interface gateways (in towers 100₃o-100₃₈) . Accordingly, the listening time slot IS for the non-interface gateway in tower 100₃₄ is [(2x9-5-1) mod 11] + 1 = 2. That is, as shown in Figure 2b, the current or normal time slot assigned to the non-interface gateway in tower IOO34 is T5, and its time slot for listening for the reverse transmis- sion is T2. Similarly, the listening time slot IS for the non-interface gateway in tower IOO35 is [ (2x9-6-1) mod 11] + 1 = 1. That is, as shown in Figure 2c, the current or normal time slot assigned to the non- interface gateway in tower IOO35 is T6, and its time slot for listening for the reverse transmission is Tl .

In the embodiment of Figure 2c, the super- frame is an odd number (11) . In a gateway in which the difference between the assigned CS and the calculated IS is 3, it is determined to delay forwarding a re- ceived reverse transmission by two time slots, step 207. More specifically, in the embodiment of Figure 2c, this applies to the gateway in the tower IOO34, for which the assigned CS is T5, and the calculated IS is T2, i.e. the difference between the assigned CS and the calculated IS is 5-2=3. As shown in Figure 2c, the gateway in the tower IOO34 delays forwarding its re- ceived reverse transmission by two time slots, i.e. to time slot T5 instead of time slot T3 ,

The exemplary embodiments can include, for example, any suitable wireless devices, and the like, capable of performing the processes of the exemplary embodiments. The devices and subsystems of the exemplary embodiments can communicate with each other using any suitable protocol and can be implemented using one or more programmed computer systems or devices.

One or more interface mechanisms can be used with the exemplary embodiments, including, for example, Internet access, telecommunications in any suitable form (e.g., voice, modem, and the like), wireless communications media, and the like. For example, employed communications networks or links can include one or more wireless communications networks, cellular communications networks, 3G communications networks, Public Switched Telephone Network (PSTNs), Packet Data Networks (PDNs), the Internet, intranets, a combination thereof, and the like.

Embodiments of the present invention may be implemented in software, hardware, application logic or a combination of software, hardware and application logic. In an example embodiment, the application logic, software or instruction set is maintained on any one of various conventional computer-readable media. In the context of this document, a "computer-readable medium" may be any media or means that can contain, store, communicate, propagate or transport the instructions for use by or in connection with an instruction execution system, apparatus, or device, such as a computer. A computer-readable medium may comprise a computer-readable storage medium that may be any media or means that can contain or store the instructions for use by or in connection with an instruction execution system, apparatus, or device, such as a computer. The exemplary embodiments can store information relating to various processes described herein. This information can be stored in one or more memories, such as a hard disk, optical disk, magneto-optical disk, RAM, and the like. One or more databases can store the information used to implement the exemplary embodiments of the present inventions. The databases can be organized using data structures (e.g., records, tables, arrays, fields, graphs, trees, lists, and the like) included in one or more memories or storage de- vices listed herein. The processes described with re^¬ spect to the exemplary embodiments can include appropriate data structures for storing data collected and/or generated by the processes of the devices and subsystems of the exemplary embodiments in one or more databases.

All or a portion of the exemplary embodiments can be conveniently implemented using one or more gen^¬ eral purpose processors, microprocessors, digital signal processors, micro-controllers, and the like, pro- grammed according to the teachings of the exemplary embodiments of the present inventions, as will be appreciated by those skilled in the computer and/or software art(s) . Appropriate software can be readily prepared by programmers of ordinary skill based on the teachings of the exemplary embodiments, as will be appreciated by those skilled in the software art. In addition, the exemplary embodiments can be implemented by the preparation of application-specific integrated circuits or by interconnecting an appropriate network of conventional component circuits, as will be appreciated by those skilled in the electrical art(s). Thus, the exemplary embodiments are not limited to any specific combination of hardware and/or software.

Stored on any one or on a combination of com- puter readable media, the exemplary embodiments of the present inventions can include software for controlling the components of the exemplary embodiments, for driving the components of the exemplary embodiments, for enabling the components of the exemplary embodiments to interact with a human user, and the like. Such software can include, but is not limited to, device drivers, firmware, operating systems, development tools, applications software, and the like. Such computer readable media further can include the computer program of an embodiment of the present inventions for performing all or a portion (if processing is distributed) of the processing performed in implementing the inventions. Computer code devices of the exemplary em^¬ bodiments of the present inventions can include any suitable interpretable or executable code mechanism, including but not limited to scripts, interpretable programs, dynamic link libraries (DLLs) , Java classes and applets, complete executable programs. Common Object Request Broker Architecture (CORBA) objects, and the like. Moreover, parts of the processing of the exemplary embodiments of the present inventions can be distributed for better performance, reliability, cost, and the like.

As stated above, the components of the exemplary embodiments can include computer readable medium or memories for holding instructions programmed according to the teachings of the present inventions and for holding data structures, tables, records, and/or other data described herein. Computer readable medium can include any suitable medium that participates in providing instructions to a processor for execution. Such a medium can take many forms, including but not limited to, non-volatile media, volatile media, transmission media, and the like. Non-volatile media can include, for example, optical or magnetic disks, magneto-optical disks, and the like. Volatile media can include dynamic memories, and the like. Transmission media can include coaxial cables, copper wire, fiber optics, and the like. Transmission media also can take the form of acoustic, optical, electromagnetic waves, and the like, such as those generated during radio frequency (RF) communications, infrared (IR) data communications, and the like. Common forms of computer- readable media can include, for example, a floppy disk, a flexible disk, hard disk, magnetic tape, any other suitable magnetic medium, a CD-ROM, CD±R, CD+RW, DVD, DVD-RAM, DVD±RW, DVD+R, HD DVD, HD DVD-R, HD DVD-RW, HD DVD-RAM, Blu-ray Disc, any other suitable optical medium, punch cards, paper tape, optical mark sheets, any other suitable physical medium with patterns of holes or other optically recognizable indicia, a RAM, a PROM, an EPROM, a FLASH-EPROM, any other suitable memory chip or cartridge, a carrier wave or any other suitable medium from which a computer can read.

If desired, the different functions discussed herein may be performed in a different order and/or concurrently with each other.

While the present inventions have been described in connection with a number of exemplary embodiments, and implementations, the present inventions are not so limited, but rather cover various modifications, and equivalent arrangements, which fall within the purview of prospective claims.

Claims

WHAT IS CLAIMED IS :

1. A method, comprising:

detecting a failure in an interface gateway of a local section of a wireless surveillance sensory data transmission network, said local section compris^¬ ing said interface gateway and a number of non- interface gateways arranged in a chain topology with said interface gateway being a destination for hop-by- hop transmission of wireless surveillance sensory data in said local section, and said interface gateway comprising a communication interface for communicating said wireless surveillance sensory data to an external data network; and

in response to said detected failure, determining to initialize a reverse transmission of information related to said hop-by-hop transmission of wireless surveillance sensory data, said reverse transmission to be performed hop-by-hop from the non- interface gateway in which the failure was detected to at least part of the remaining non-interface gateways in said local section.

2. The method according to claim 1, wherein the transmissions are of time-division multiplexing type, the method further comprising:

calculating, in a non-interface gateway, a time slot for listening for said reverse transmission according to IS = 2xSI - CS, wherein IS is said time slot for listening,- SI is the number of the non- interface gateways in the local section involved in said reverse transmission, and CS is a current time slot assigned to said non-interface gateway for said transmission of wireless surveillance sensory data in said local section.

3. The method according to claim 1, wherein the transmissions are of time-division multiplexing type, the method further comprising: calculating, in a non-interface gateway, a time slot for listening for said reverse transmission according to at least one of IS = [ (2xSI - CS - 1) mod superframe] + 1 and IS = [ (2xSI - CS) mod superframe] + 1, wherein IS is said time slot for listening, SI is the number of the non-interface gateways in the local section involved in said reverse transmission, CS is a current time slot assigned to said non-interface gateway for said transmission of wireless surveillance sensory data in said local section, and superframe is the total number of time slots in one duty cycle of said non-interface gateway.

4. The method according to claim 3, wherein said superframe is an even number, and the difference between the assigned CS and the calculated IS is one of 2 and 0, the method further comprising:

determining to delay forwarding a received reverse transmission for one time slot in said non- interface gateway.

5. The method according to claim 1 , wherein the transmissions are of time-division multiplexing type, the method further comprising:

calculating, in a non-interface gateway, a time slot for listening for said reverse transmission according to at least one of IS = [ (2xSI - CS ~ 1) mod superframe] + 1 and IS = [ (2xSI - CS) mod superframe] + 2, wherein IS is said time slot for listening, SI is the number of the non-interface gateways in the local section involved in said reverse transmission, CS is a current time slot assigned to said non-interface gateway for said transmission of wireless surveillance sensory data in said local section, and superframe is the total number of time slots in one duty cycle of said non-interface gateway.

6. The method according to claim 5, wherein said superframe is an odd number, and the difference between the assigned CS and the calculated IS is 3, the method further comprising:

determining to delay forwarding a received reverse transmission for two time slots in said non- interface gateway.

7. The method according to any of claims 2-6, wherein SI is stored in the non-interface gateways.

8. The method according to any of claims 1-7, wherein the information related to said hop-by-hop transmission of wireless surveillance sensory data comprises at least one of said wireless surveillance sensory data and an alarm about said detected failure.

9. The method according to any of claims 1-8, wherein the surveillance sensory data relates to one of an electrical power transmission line and a traffic line .

10. An apparatus, comprising:

at least one processor; and

at least one memory including computer program code,

the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to perform:

detecting a failure in an interface gateway of a local section of a wireless surveillance sensory data transmission network, said local section comprising said interface gateway and a number of non- interface gateways arranged in a chain topology with said interface gateway being a destination for hop-by- hop transmission of wireless surveillance sensory data in said local section, and said interface gateway comprising a communication interface for communicating said wireless surveillance sensory data to an external data network; and

in response to said detected failure, initializing a reverse transmission of information related to said hop-by-hop transmission of wireless sur- veillance sensory data, said reverse transmission to be performed, hop-by-hop from the non-interface gateway in which the failure was detected to at least part of the remaining non-interface gateways in said local section.

11. The apparatus according to claim 10, wherein the transmissions are of time-division multi^¬ plexing type, and the at least one memory and the computer program code are further configured to, with the at least one processor, cause the apparatus to further perform :

calculating, in a non-interface gateway, a time slot for listening for said reverse transmission according to IS = 2xSI - CS, wherein IS is said time slot for listening, SI is the number of the non- interface gateways in the local section involved in said reverse transmission, and CS is a current time slot assigned to said non-interface gateway for said transmission of wireless surveillance sensory data in said local section.

12. The apparatus according to claim 10, wherein the transmissions are of time-division multiplexing type, and the at least one memory and the computer program code are further configured to, with the at least one processor, cause the apparatus to further perform :

calculating, in a non-interface gateway, a time slot for listening for said reverse transmission according to at least one of IS = [ (2xSI - CS - 1) mod superframe] + 1 and IS = [ (2xSI - CS) mod superframe] + 1, wherein IS is said time slot for listening, SI is the number of the non-interf ce gateways in the local section involved in said reverse transmission, CS is a current time slot assigned to said non-interf ce gate- way for said transmission of wireless surveillance sensory data in said local section, and superframe is the total number of time slots in one duty cycle of said non-interface gateway.

13. The apparatus according to claim 12, wherein said superframe is an even number, the difference between the assigned CS and the calculated IS is one of 2 and 0, and the at least one memory and the computer program code are further configured to, with the at least one processor, cause the apparatus to further perform:

14. The apparatus according to claim 10, wherein the transmissions are of time-division multiplexing type, and the at least one memory and the computer program code are further configured to, with the at least one processor, cause the apparatus to further perform :

calculating, in a non-interface gateway, a time slot for listening for said reverse transmission according to at least one of IS = [ {2xSI - CS - 1) mod superframe] + 1 and IS = [ (2xSl - CS) mod superframe] + 2, wherein IS is said time slot for listening, SI is the number of the non-interface gateways in the local section involved in said reverse transmission, CS is a current time slot assigned to said non-interface gate^¬ way for said transmission of wireless surveillance sensory data in said local section, and superframe is the total number of time slots in one duty cycle of said non-interface gateway.

15. The apparatus according to claim 14, wherein said superframe is an odd number, the difference between the assigned CS and the calculated IS is 3, and the at least one memory and the computer pro^¬ gram code are further configured to, with the at least one processor, cause the apparatus to further perform: determining to delay forwarding a received reverse transmission for two time slots in said non- interface gateway.

16. The apparatus according to any of claims 11-15, wherein SI is stored in the non-interface gateways .

17. The apparatus according to any of claims 10-16, wherein the information related to said hop-by- hop transmission of wireless surveillance sensory data comprises at least one of said wireless surveillance sensory data and an alarm about said detected failure.

18. The apparatus according to any of claims 10-17, wherein the surveillance sensory data relates to one of an electrical power transmission line and a traffic line.

19. A computer program, comprising code adapted to cause the following when executed on a da^¬ ta-processing system:

in response to said detected failure, determining to initialize a reverse transmission of information related to said hop-by-hop transmission of wireless surveillance sensory data, said reverse transmission to be performed hop-by-hop from the non- interface gateway in which the failure was detected to at least part of the remaining non-interface gateways in said local section. 20- The computer program according to claim 19, wherein the computer program is stored on a computer readable medium.