Beam finding procedure

Beam finding process technical field

[0001] The embodiments presented herein relate to methods, wireless transceiver devices, computer programs, and computer program products for using beams to receive transmission resources.

Background technique

[0002] In a communication network, for a given communication protocol, its parameters, and the physical environment in which the communication network is deployed, it may be challenging to obtain good performance and capacity.

[0003] For example, for future generations of mobile communication systems, many frequency bands under different carrier frequencies may be required. For example, a low frequency band of this kind may be required to achieve sufficient network coverage for wireless transceiver devices, and a higher frequency band (for example, at millimeter wavelength (mmW), that is close to and above 30 GHz) may be required to achieve the required Network capacity. Generally speaking, at high frequencies, the propagation properties of the wireless channel are more challenging, and beamforming may be required at both the access node and the wireless transceiver device of the network to achieve a sufficient link budget.

[0004] The wireless transceiver device may implement beamforming by means of analog beamforming, digital beamforming, or hybrid beamforming. Each implementation has its advantages and disadvantages. The digital beamforming implementation is the most flexible of the three, but the cost is also the highest, because it requires a large number of radio chains and baseband chains. Compared with the implementation of digital beamforming, the implementation of analog beamforming has the lowest flexibility but lower manufacturing cost, because the number of radio chains and baseband chains is reduced. The hybrid beamforming implementation is a compromise between the analog and digital beamforming implementations. As the skilled person understands, different implementations will be required according to the cost and performance requirements of different wireless transceiver devices.

[0005] When the wireless transceiver device uses analog beamforming, the wireless transceiver device may be challenging in the following aspects: According to a given signal quality standard, determine whether the currently used beam generated by using analog beamforming is a good beam; Or if there are other beams generated by analog beamforming, whether these beams perform significantly better according to a given signal quality standard. In order to evaluate whether any other such beams are better, for example, a beam-finding process using beam reference signals (BRS) can be used. However, performing such a process usually requires relatively more overhead signaling between the access node and the wireless transceiver device, and therefore will temporarily reduce the performance in the network.

[0006] Therefore, there is a need for an improved beam finding process.

Summary of the invention

[0007] One goal of the embodiments herein is to achieve effective beam finding for wireless transceiver devices.

[0008] According to the first aspect, a method for receiving transmission resources using beams is proposed. The method is performed by a wireless transceiver device. The method includes receiving a current transmission resource using a first transmission format from an access node using a first beam. The method includes sending to the access node an indicator to use a second transmission format for subsequent transmission resources to be sent to the wireless transceiver device. The method includes using, at least in part, a candidate beam to receive the subsequent transmission resource, wherein the candidate beam is different from the first beam.

[0009] Advantageously, when beams are used, this provides efficient reception of transmission resources. During beam seeking for the wireless transceiver device, such efficient reception of transmission resources can be used.

[0010] Advantageously, this method enables the wireless transceiver device to test any number of candidate beams in order to improve the chain

Road budget, and increase throughput in terms of bits per second without major overhead.

[0011] According to a second aspect, a wireless transceiver device for receiving transmission resources using beams is proposed. The wireless transceiver device includes a processing circuit. The processing circuit is configured to cause the wireless transceiver device to use the first beam to receive the current transmission resource using the first transmission format from the access node. The processing circuit is configured to cause the wireless transceiver device to send to the access node an indicator to use a second transmission format for subsequent transmission resources to be sent to the wireless transceiver device. The processing circuit is configured to cause the wireless transceiver device to at least partially use a candidate beam to receive the subsequent transmission resource, wherein the candidate beam is different from the first beam.

[0012] According to a third aspect, a wireless transceiver device for receiving transmission resources using beams is proposed. The wireless transceiver device includes a processing circuit and a computer program product. The computer program product stores instructions that, when executed by the processing circuit, cause the wireless transceiver device to perform operations or steps. The operation or step causes the wireless transceiver device to use the first beam to receive the current transmission resource using the first transmission format from the access node. The operation or step causes the wireless transceiver device to send to the access node an indicator to use the second transmission format for subsequent transmission resources to be sent to the wireless transceiver device. The operation or step causes the wireless transceiver device to at least partially use a candidate beam to receive the subsequent transmission resource, wherein the candidate beam is different from the first beam.

[0013] According to a fourth aspect, a wireless transceiver device for receiving transmission resources using a beam is proposed. The wireless transceiver device includes a receiving module configured to receive a current transmission resource using a first transmission format from an access node using a first beam. The wireless transceiver device includes a sending module configured to send to the access node an indicator that uses a second transmission format for subsequent transmission resources to be sent to the wireless transceiver device. The wireless transceiver device includes a receiving module configured to at least partially use a candidate beam to receive the subsequent transmission resource, wherein the candidate beam is different from the first beam.

[0014] According to a fifth aspect, a computer program for receiving transmission resources using a beam is proposed. The computer program includes computer program code that, when run on a wireless transceiver device, causes the wireless The transceiver device performs the method according to the first aspect.

[0015] According to a sixth aspect, a computer program product is proposed, which includes the computer program according to the fifth aspect and a computer-readable storage medium on which the computer program is stored. The computer-readable storage medium may be a non-transitory computer-readable storage medium.

[0016] It should be noted that any feature of the first, second, third, fourth, fifth, and sixth aspects can be applied to any other aspect where appropriate. Likewise, any advantages of the first aspect can be equally applied to the second, third, fourth, fifth, and/or sixth aspects, respectively, and vice versa. Other objectives, characteristics and advantages of the appended embodiments will be apparent from the following detailed disclosure, appended dependent claims and drawings.

[0017] Generally, all terms used in the claims are interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a/a/the element, device, component, component, step, etc." will be publicly interpreted as referring to at least one example of the element, device, component, component, step, etc., unless explicitly stated otherwise. The steps of any method disclosed herein need not be executed in the exact order disclosed, unless explicitly stated.

Description of the drawings

[0018] The concept of the present invention will now be described by way of example with reference to the accompanying drawings, which are:

[0019] FIG. 1 is a schematic diagram showing a communication network according to an embodiment;

[0020] FIGS. 2, 3, and 4 are flowcharts of methods according to embodiments;

[0021] FIG. 5 is a schematic diagram showing functional units of a wireless transceiver device according to an embodiment;

[0022] FIG. 6 is a schematic diagram showing functional modules of a wireless transceiver device according to an embodiment; and

[0023] FIG. 7 shows an example of a computer program product including a computer-readable storage medium according to an embodiment.

Detailed ways

[0024] The concept of the present invention will now be described more fully below with reference to the accompanying drawings, in which certain embodiments of the concept of the present invention are shown. However, the concept of the present invention can be embodied in many different forms, and should not be construed as being limited to the embodiments given here; on the contrary, these embodiments are provided by way of examples to make this disclosure detailed and complete, and will The scope of the concept of the present invention is fully conveyed to those skilled in the art. In this, the same numbers refer to the same elements. Any steps or features shown by dashed lines should be considered optional.

[0025] FIG. 1(a) is a schematic diagram showing a communication network 100a (left side) and a corresponding downlink (DL) subframe (right side) according to the prior art. The DL subframe includes demodulation and measurement Single reference signal (RS).

[0026] The communication network 100a includes an access node 300, which provides network access to the wireless transceiver device 200. The access node 300 may be any one of the following: a wireless access network node, a wireless base station, a base transceiver station, a node B, an evolved node B, or an access point. The wireless transceiver device 200 may be any of the following: a portable wireless device, a mobile station, a mobile phone, a cell phone, a wireless local loop phone, a user equipment (UE), a smart phone, a laptop computer, a tablet computer, or a wireless sensor.

[0027] The wireless transceiver device 200 transmits and receives signals to and from the access node 300 in the beam 110a denoted as B1 during the entire subframe. Assume that the wireless transceiver device 200 tries to evaluate another candidate beam 110b denoted as B2 (for example, by measuring the reference symbol received power (RSRP) in the candidate beam) for transmission to and reception from the access node 300. However, because the downlink subframe only includes a single reference signal for demodulation and measurement, the wireless transceiver device 200 cannot temporarily switch to another candidate beam during the subframe in order to evaluate the candidate beam in a reliable manner (by Measurement reference symbol).

[0028] The embodiments disclosed herein enable the wireless transceiver device 200 to evaluate the candidate beam 110b. Generally speaking, and as will be further disclosed below, the wireless transceiver device 200 transmits to the access node 300 the transmission format that enables the wireless transceiver device 200 to evaluate at least one candidate beam 110b (by measuring the reference symbol) in a reliable manner The indication (explicit or implicit).

[0029] Therefore, the embodiments disclosed herein relate to a mechanism for using beams 110a, 110b to receive transmission resources. In order to obtain this mechanism, a wireless transceiver device 200, a method executed by the wireless transceiver device 200, and a computer program product are provided. The computer program product includes, for example, code in the form of a computer program, which when running on the wireless transceiver device 200 At this time, the wireless transceiver device 200 is caused to execute the method.

[0030] FIGS. 2 and 3 are flowcharts illustrating an embodiment of a method for using beams 110a, 110b to receive transmission resources. These methods are executed by the wireless transceiver device 200. These methods are advantageously provided as a computer program 720.

[0031] Reference is now made to FIG. 2 which illustrates a method performed by the wireless transceiver device 200 for receiving transmission resources using beams 110a, 110b according to one embodiment.

[0032] S102: The wireless transceiver device 200 uses the first beam 110a to receive the current transmission resource using the first transmission format from the access node 300.

[0033] Assume that the wireless transceiver device 200 tries to evaluate another candidate beam 110b for transmission to and reception from the access node 300, but tries to avoid the above-mentioned problem. Therefore, the wireless transceiver device 200 is configured to perform step S106:

[0034] S106: The wireless transceiver device 200 sends to the access node 300 the information to be sent to the wireless transceiver device

The subsequent transmission resources of 200 use the indicator of the second transmission format. Examples of such indicators will be provided below. An example of the difference between the first transmission format and the second transmission format will be provided below.

[0035] Assume that the access node 300 receives the instruction, and in response thereto, uses the second transmission format to send subsequent transmission resources to the wireless transceiver device 200. Therefore, the wireless transceiver device 200 is configured to perform step S108:

[0036] S108: The wireless transceiver device 200 at least partially uses the candidate beam 110b to receive subsequent transmission resources. The candidate beam 110b is different from the first beam 110a. "Different" means that the candidate beam 110b has at least a pointing direction and/or polarization different from that of the first beam 110a, and may also have a different beam width.

[0037] Embodiments related to further details performed by the wireless transceiver device 200 for receiving transmission resources using the beams 110a, 110b will now be disclosed.

[0038] Reference is now made to FIG. 3, which illustrates a method performed by the wireless transceiver device 200 for receiving transmission resources using the beams 110a, 110b according to other embodiments. It is assumed that steps S102, S106, and S108 are performed as described above with reference to FIG. 2, and therefore, repeated descriptions thereof are omitted.

[0039] FIG. 1(b) is a schematic diagram showing a communication network 100b (left side) and a corresponding downlink (DL) subframe (right side) according to an embodiment, the DL subframe includes demodulation and measurement Of two single reference signals (RS). Figure 1(b) shows an embodiment of the wireless transceiver device 200 using two different beams 110a, 110b to perform (analog) beamforming, one of which is the first beam 110a (denoted as B1), and the other beam It is the candidate beam 110b (denoted as B2). The right side of FIG. 1(b) shows how the wireless transceiver device 200 switches between the two beams B1 and B2 in order to evaluate the performance of the candidate beam B2. During the reception subframe, the wireless transceiver device 200 therefore switches from receiving using the beam B1 to receiving using the beam B2, so as to use B2 in the time/frequency resource containing at least one reference signal. Then, the wireless transceiver device 200 can evaluate whether the beam B2 is more suitable than the beam B1. Once the evaluation is completed, the wireless transceiver device 200 switches to the best beam (hence the beam B1 or B2). Before the evaluation is completed, the wireless transceiver device 200 uses the first beam B1.

[0040] Although FIG. 1 relates to beamforming using two different beams 110a, 110b, the embodiments disclosed herein are not limited to the use of the first beam 110a and one candidate beam 110b; the embodiments disclosed herein are applicable to any number The candidate beam 110b, and therefore the wireless transceiver device 200 may be configured to evaluate a plurality of such candidate beams 110b during the reception of subsequent transmission resources using the second transmission format_o

[0041] When the wireless transceiver device 200 should send the instruction and therefore perform step S106, there may be different triggers. For example, the wireless transceiver device 200 may be configured to send the indication when the signal strength has fallen below a threshold signal strength value, has fallen at a rate higher than the threshold rate value, or the rank ratio in the radio channel is more than the threshold. The value is worse. Therefore, according to one embodiment, the wireless transceiver device 200 is configured to perform step S104:

[0042] S104: The wireless transceiver device 200 obtains an indication of at least one of the signal strength reduction and the channel rank of the transmission from the access node 300, and the indicator for using the second transmission format is transmitted in response thereto .

[0043] For example, the wireless transceiver device 200 may be configured to periodically (eg, periodically) evaluate candidate beams in order to investigate whether there is a beam better than the currently used beam. Therefore, according to one embodiment, the indication in step S106 is sent according to the schedule.

[0044] The wireless transceiver device 200 may have different ways to indicate to the access node to use the second transmission format.

[0045] According to one embodiment, explicit signaling is used, which may be, for example, signals known at both the wireless transceiver device 200 and the access node 300, so that the access node 300 knows that the wireless transceiver device 200 will Perform beam training, and therefore use the transmission format accordingly. Therefore, according to one embodiment, the indicator sent in step S106 requests the access node 300 to enable the wireless transceiver device 200 to evaluate the candidate beam 110b. For example, the indicator may be a dedicated candidate beam evaluation message.

[0046] According to one embodiment, using implicit signaling, for example, the wireless transceiver device 200 may signal a reduced signal-to-interference and noise ratio (SINR), so that the access node 300 can increase the density of the reference signal and use a stronger Data signal encoding. Therefore, an example of implicit signaling is that the wireless transceiver device 200 purposefully signals a falsely reduced SINR, which can cause the access node 300 to use an increased reference signal density and a reduced modulation and coding scheme (MCS) . Therefore, according to an embodiment, the indicator sent in step S106 is a message including at least one of a channel quality indicator and a rank indicator.

[0047] There may be different ways to distinguish the second transmission format from the first transmission format. According to certain aspects, the wireless transceiver device 200 enables more measurement opportunities in the second transmission format than in the first transmission format. According to one embodiment, the wireless transceiver device 200 is provided with more measurement opportunities in the second transmission format than in the first transmission format, for example to measure the reference signal. Therefore, according to this embodiment, the second transmission format has a higher reference signal density than the first transmission format. 1 (a) and (6), the wireless transceiver device 200 is provided with a single measurement opportunity in the DL subframe of FIG. 1 (a), and is provided with two measurement opportunities in the DL subframe of FIG. 1(6).

[0048] Therefore, one purpose of the access node 300 increasing the reference symbol density is to thereby allow the wireless transceiver device 200 to evaluate the candidate beam 110b more frequently. One reason for lowering the MCS is that in the case where the candidate beam 110b is worse than the original first beam 110a, the SINR of the downlink data signal will be degraded during the beam search process, and therefore more robust coding of the data signal is required , So that the wireless transceiver device 200 correctly demodulates the data signal.

[0049] For example, assuming that one DL subframe corresponds to a transmission resource, the access node 300 may therefore transmit the reference signal more frequently in the second transmission format than in the first transmission format. Therefore, according to an embodiment, the access node 300 transmits more reference signals for each transmission resource in the second transmission format than in the first transmission format.

[0050] The wireless transceiver device 200 has knowledge about time/frequency resources containing reference signals. This configuration of the reference signal can be obtained by the wireless transceiver device 200 from the access node 300 along with its downlink allocation on the control channel.

[0051] The change of the transmission format means that the access node 300 changes at least one of the following: reference symbol density in time and/or frequency (for example, channel state information-reference signal (CSI-RS), demodulation reference signal (DMRS), Position reference signal (PRS), beam reference signal (BRS), etc.), and/or MCS. Specifically, according to one embodiment, the second transmission format has a more robust coding and modulation scheme and/or a more robust rank than the first transmission format.

[0052] The evaluation of the candidate beam may be, for example, by measuring the received signal strength, the absolute square of the channel estimation, the MSE (Mean Square Error) in the channel estimation, the MMSE (Minimum Mean Square Error) in the demodulation, and the SNR by the wireless transceiver device 200. , Or SINR to perform. That is, according to certain aspects, the wireless transceiver device 200 evaluates the performance metric for the candidate beam 110b. Therefore, according to an embodiment, the wireless transceiver device 200 is configured to perform step S110:

[0053] S110: The wireless transceiver device 200 evaluates the candidate beam 110b by comparing the performance metric between the candidate beam 110b and the first beam 110a_o

[0054] When the candidate beam 110b has a better performance metric than the first beam 110a, the first beam 110a may be replaced by the candidate beam 110b. Therefore, according to an embodiment, the wireless transceiver device 200 is configured to perform step S112:

[0055] S112: When the candidate beam 110b has a better performance metric than the first beam 110a, the wireless transceiver device

200 replaces the first beam 110a with the candidate beam 110b.

[0056] The performance metric may be based on the received power of the current transmission and subsequent transmissions.

[0057] In step S108, the wireless transceiver device 200 may have different ways to determine in which candidate beam 110b to receive the transmission resource. For example, the candidate beam 110b may be selected based on the following items: previous statistical information, the physical structure of the wireless transceiver device 200, the antenna of the wireless transceiver device 200, and the like. Therefore, according to one embodiment, the candidate beam 110b has a pointing direction and a beam width, and at least one of the pointing direction and the beam width is based on at least one of measurement statistics and physical properties of the wireless transceiver device 200.

[0058] There may be different examples for how many transmission resources will use the second transmission format. For example, the second transmission format can be used only temporarily. Therefore, according to one embodiment, the second transmission format is only used in subsequent transmission resources.

[0059] There are different transmission resource examples. Generally speaking, transmission resources have duration in time and frequency. According to one embodiment, each transmission resource corresponds to a single orthogonal frequency division multiplexing (OFDM) symbol, a single subframe, or a single transmission time interval (TTI). However, alternatively, each transmission resource corresponds to multiple OFDM symbols, subframes, or TTIs.

[0060] FIG. 4 is a flowchart of a specific embodiment performed by the wireless transceiver device 200 and the access node 300 to use the beams 110a, 110b to receive transmission resources.

[0061] Step S201: The wireless transceiver device 200 determines and evaluates one or more candidate beams to be used during data transmission and/or reception. The wireless transceiver device 200 signals to the access node 300 to change to a transmission format that facilitates beam searching at the wireless transceiver device 200. One way to implement step S201 is to perform any one of steps S102, S104, and S106.

[0062] Step S202: The access node 300 changes the transmission format during the transmission scheduled for the wireless transceiver device 200.

[0063] Step S203: The wireless transceiver device 200 receives a transmission from the access node 300, and during at least one time/frequency resource containing a reference symbol, the wireless transceiver device 200 uses the candidate beam 110b for reception. When the wireless transceiver device 200 has received reference signals in different beams 110a, 110b, it can evaluate which beam is the most preferred beam according to any of the evaluation metrics listed above. One way to implement step S203 is to perform any one of steps S108 and S110.

[0064] Step S204: The wireless transceiver device 200 selects the best beam based on the evaluation in step S203, and then uses the beam for future transmission and/or reception. Step S201 can be entered again periodically or as needed. One way to implement step S204 is to perform step S112_o

[0065] FIG. 5 schematically illustrates the components of a wireless transceiver device 200 according to an embodiment in terms of multiple functional units. Use any combination of one or more of the following to provide the processing circuit 210: a suitable central processing unit (CPU), multiprocessor, microcontroller, digital signal processor (DSP), etc., which can execute storage in, for example, the form The software instructions in the computer program product 710 (as in FIG. 7) of the storage medium 230. The processing circuit 210 may also be provided as at least one application specific integrated circuit (ASIC) or field programmable gate array (FPGA).

[0066] Specifically, the processing circuit 210 is configured to perform a set of operations, or steps S102-S112, S201, S203, S204, or steps S102-S112, S201, S203, S204 for the wireless transceiver device 200, as described above. For example, the storage medium 230 may store the set of operations, and the processing circuit 210 may be configured to retrieve the set of operations from the storage medium 230, so that the wireless transceiver device 200 can perform the set of operations. The set of operations can be provided as a set of executable instructions.

[0067] Therefore, the processing circuit 210 is thus arranged to perform the method as disclosed herein. The storage medium 230 may also include

This includes a persistent storage device, which can be, for example, any one or combination of magnetic memory, optical memory, solid-state memory, or even remotely mounted memory. The wireless transceiver device 200 may further include a communication interface 220, which is at least configured to communicate with the access node 300. Therefore, the communication interface 220 may include one or more transmitters and receivers, which include analog and digital components. The processing circuit 210 controls the general operation of the wireless transceiver device 200, for example, by sending data and control signals to the communication interface 220 and the storage medium 230, receiving data and reports from the communication interface 220, and obtaining data and control signals from the storage medium 230. instruction. Other components and related functions of the wireless transceiver device 200 are omitted so as not to obscure the concepts presented here.

[0068] FIG. 6 schematically shows the components of the wireless transceiver device 200 according to an embodiment in accordance with a plurality of functional modules. The wireless transceiver device 200 of FIG. 6 includes a plurality of functional modules: a receiving module 210a configured to perform step S102, a sending module 210c configured to perform step S106, and a receiving module 210d configured to perform step S108. The wireless transceiver device 200 of FIG. 6 may also include multiple optional functional modules, such as any one of the following: an obtaining module 210b configured to perform step S104, an evaluation module 210e configured to perform step S110, and configured It is the replacement module 210f that executes step S112. Generally speaking, each functional module 210a-210f can be implemented only by hardware in one embodiment, or by means of software in another embodiment, that is, the latter embodiment has computer program instructions stored on the storage medium 230. The computer program instructions when running on the processing circuit cause the wireless transceiver device 200 to perform the corresponding steps mentioned above in conjunction with FIG. 6. It should also be mentioned that although modules correspond to multiple parts of a computer program, They do not need to be separate modules in a computer program, but the way they are implemented in software depends on the programming language used. Preferably, one or more or all of the functional modules 210a-210f may be implemented by the processing circuit 210 (possibly in cooperation with the functional units 220 and/or 230). Therefore, the processing circuit 210 may be configured to retrieve the instructions provided by the functional modules 210a-210f from the storage medium 230 and execute these instructions, thereby performing any steps as disclosed herein.

[0069] The wireless transceiver device 200 may be provided as a stand-alone device or part of at least one other device. For example, the wireless transceiver device 200 may be implemented in an access node or a wireless device, be a part of an access node or a wireless device, or be co-located with an access node or a wireless device. Therefore, according to certain aspects, there is provided an access node and/or wireless device including the wireless transceiver device 200 as disclosed herein.

[0070] In addition, the first part of the instructions executed by the wireless transceiver device 200 may be executed in the first device, and the second part of the instructions executed by the wireless transceiver device 200 may be executed in the second device; disclosed herein The embodiments of are not limited to any specific number of devices on which instructions executed by the wireless transceiver device 200 can be executed. Therefore, the method according to the embodiments disclosed herein is suitable for being executed by the wireless transceiver device 200 residing in a cloud computing environment. Therefore, although a single processing circuit 210 is shown in FIG. 5, the processing circuit 210 may be distributed among multiple devices or nodes. The same applies to the functional modules 210a-210f of FIG. 6 and the computer program 720 of FIG. 7 (see below).

[0071] FIG. 7 shows an example of a computer program product 710 that includes a computer-readable storage medium 730. A computer program 720 can be stored on the computer-readable storage medium 730, and the computer program 720 can cause the processing circuit 210 and the entities and devices operatively coupled thereto (for example, the communication interface 220 and the storage medium 230) to execute the processes described herein The method described in the embodiment. Therefore, the computer program 720 and/or the computer program product 710 may provide means for performing any of the steps as disclosed herein.

[0072] In the example of FIG. 7, the computer program product 710 is shown as an optical disc, such as a CD (Compact Disc) or DVD (Digital Versatile Disc) or Blu-ray Disc. The computer program product 710 can also be implemented as a memory, such as random access memory (RAM), read only memory (ROM), erasable programmable read only memory (EPROM), or electrically erasable programmable read only memory ( EEPROM) and more specifically implemented as USB (Universal Serial Bus) memory or flash memory (e.g. compact

Type flash memory) and other non-volatile storage media in external storage devices. Therefore, although the computer program 720 is schematically shown here as a track on the optical disc shown, the computer program 720 may be stored in any manner suitable for the computer program product 710.

[0073] The concept of the present invention is mainly described above with reference to several embodiments. However, as easily understood by those skilled in the art, other embodiments than the embodiments disclosed above are equally possible within the scope of the concept of the present invention defined by the appended patent claims.